<?xml version="1.0" encoding="US-ASCII"?>
<!--XBRL Document Created with Wdesk from Workiva-->
<!-- -->
<link:linkbase xsi:schemaLocation="http://www.xbrl.org/2003/linkbase http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd" xmlns:link="http://www.xbrl.org/2003/linkbase" xmlns:xbrldt="http://xbrl.org/2005/xbrldt" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
  <link:roleRef roleURI="http://ucbi.com/role/AccountingPolicies" xlink:href="ucbi-20190930.xsd#AccountingPolicies" xlink:type="simple" />
  <link:roleRef roleURI="http://ucbi.com/role/AccountingPoliciesPolicies" xlink:href="ucbi-20190930.xsd#AccountingPoliciesPolicies" xlink:type="simple" />
  <link:roleRef roleURI="http://ucbi.com/role/AccountingStandardsUpdatesAndRecentlyAdoptedStandards" xlink:href="ucbi-20190930.xsd#AccountingStandardsUpdatesAndRecentlyAdoptedStandards" xlink:type="simple" />
  <link:roleRef roleURI="http://ucbi.com/role/AccountingStandardsUpdatesAndRecentlyAdoptedStandardsNarrativeDetails" xlink:href="ucbi-20190930.xsd#AccountingStandardsUpdatesAndRecentlyAdoptedStandardsNarrativeDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://ucbi.com/role/Acquisitions" xlink:href="ucbi-20190930.xsd#Acquisitions" xlink:type="simple" />
  <link:roleRef roleURI="http://ucbi.com/role/AcquisitionsAcquiredLoanAndLeasePortfolioAtAcquisitionDateDetails" xlink:href="ucbi-20190930.xsd#AcquisitionsAcquiredLoanAndLeasePortfolioAtAcquisitionDateDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://ucbi.com/role/AcquisitionsAcquisitionDateFairValueOfPurchasedAssetsAndLiabilitiesDetails" xlink:href="ucbi-20190930.xsd#AcquisitionsAcquisitionDateFairValueOfPurchasedAssetsAndLiabilitiesDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://ucbi.com/role/AcquisitionsNarrativeDetails" xlink:href="ucbi-20190930.xsd#AcquisitionsNarrativeDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://ucbi.com/role/AcquisitionsProFormaInformationDetails" xlink:href="ucbi-20190930.xsd#AcquisitionsProFormaInformationDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://ucbi.com/role/AcquisitionsTables" xlink:href="ucbi-20190930.xsd#AcquisitionsTables" xlink:type="simple" />
  <link:roleRef roleURI="http://ucbi.com/role/AssetsAndLiabilitiesMeasuredAtFairValue" xlink:href="ucbi-20190930.xsd#AssetsAndLiabilitiesMeasuredAtFairValue" xlink:type="simple" />
  <link:roleRef roleURI="http://ucbi.com/role/AssetsAndLiabilitiesMeasuredAtFairValueAssetsAndLiabilitiesMeasuredAtFairValueOnNonrecurringBasisDetails" xlink:href="ucbi-20190930.xsd#AssetsAndLiabilitiesMeasuredAtFairValueAssetsAndLiabilitiesMeasuredAtFairValueOnNonrecurringBasisDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://ucbi.com/role/AssetsAndLiabilitiesMeasuredAtFairValueAssetsAndLiabilitiesMeasuredAtFairValueOnRecurringBasisDetails" xlink:href="ucbi-20190930.xsd#AssetsAndLiabilitiesMeasuredAtFairValueAssetsAndLiabilitiesMeasuredAtFairValueOnRecurringBasisDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://ucbi.com/role/AssetsAndLiabilitiesMeasuredAtFairValueFairValuesForOtherFinancialInstrumentsThatAreNotMeasuredAtFairValueOnRecurringBasisDetails" xlink:href="ucbi-20190930.xsd#AssetsAndLiabilitiesMeasuredAtFairValueFairValuesForOtherFinancialInstrumentsThatAreNotMeasuredAtFairValueOnRecurringBasisDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://ucbi.com/role/AssetsAndLiabilitiesMeasuredAtFairValueNarrativeDetails" xlink:href="ucbi-20190930.xsd#AssetsAndLiabilitiesMeasuredAtFairValueNarrativeDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://ucbi.com/role/AssetsAndLiabilitiesMeasuredAtFairValueQuantitativeInformationAboutLevel3FairValueMeasurementsForFairValueOnRecurringBasisDetails" xlink:href="ucbi-20190930.xsd#AssetsAndLiabilitiesMeasuredAtFairValueQuantitativeInformationAboutLevel3FairValueMeasurementsForFairValueOnRecurringBasisDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://ucbi.com/role/AssetsAndLiabilitiesMeasuredAtFairValueReconciliationForMeasurementsAtFairValueOnRecurringBasisUsingSignificantUnobservableInputsDetails" xlink:href="ucbi-20190930.xsd#AssetsAndLiabilitiesMeasuredAtFairValueReconciliationForMeasurementsAtFairValueOnRecurringBasisUsingSignificantUnobservableInputsDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://ucbi.com/role/AssetsAndLiabilitiesMeasuredAtFairValueTables" xlink:href="ucbi-20190930.xsd#AssetsAndLiabilitiesMeasuredAtFairValueTables" xlink:type="simple" />
  <link:roleRef roleURI="http://ucbi.com/role/BalanceSheetOffsettingAndRepurchaseAgreementsAccountedForAsSecuredBorrowings" xlink:href="ucbi-20190930.xsd#BalanceSheetOffsettingAndRepurchaseAgreementsAccountedForAsSecuredBorrowings" xlink:type="simple" />
  <link:roleRef roleURI="http://ucbi.com/role/BalanceSheetOffsettingAndRepurchaseAgreementsAccountedForAsSecuredBorrowingsNarrativeDetails" xlink:href="ucbi-20190930.xsd#BalanceSheetOffsettingAndRepurchaseAgreementsAccountedForAsSecuredBorrowingsNarrativeDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://ucbi.com/role/BalanceSheetOffsettingAndRepurchaseAgreementsAccountedForAsSecuredBorrowingsRepurchaseAgreementsAccountedForAsSecuredBorrowingsDetails" xlink:href="ucbi-20190930.xsd#BalanceSheetOffsettingAndRepurchaseAgreementsAccountedForAsSecuredBorrowingsRepurchaseAgreementsAccountedForAsSecuredBorrowingsDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://ucbi.com/role/BalanceSheetOffsettingAndRepurchaseAgreementsAccountedForAsSecuredBorrowingsSummaryOfAmountsOutstandingUnderMasterNettingAgreementsDetails" xlink:href="ucbi-20190930.xsd#BalanceSheetOffsettingAndRepurchaseAgreementsAccountedForAsSecuredBorrowingsSummaryOfAmountsOutstandingUnderMasterNettingAgreementsDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://ucbi.com/role/BalanceSheetOffsettingAndRepurchaseAgreementsAccountedForAsSecuredBorrowingsTables" xlink:href="ucbi-20190930.xsd#BalanceSheetOffsettingAndRepurchaseAgreementsAccountedForAsSecuredBorrowingsTables" xlink:type="simple" />
  <link:roleRef roleURI="http://ucbi.com/role/CommitmentsAndContingencies" xlink:href="ucbi-20190930.xsd#CommitmentsAndContingencies" xlink:type="simple" />
  <link:roleRef roleURI="http://ucbi.com/role/CommitmentsAndContingenciesContractualAmountOfOffBalanceSheetInstrumentsDetails" xlink:href="ucbi-20190930.xsd#CommitmentsAndContingenciesContractualAmountOfOffBalanceSheetInstrumentsDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://ucbi.com/role/CommitmentsAndContingenciesNarrativeDetails" xlink:href="ucbi-20190930.xsd#CommitmentsAndContingenciesNarrativeDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://ucbi.com/role/CommitmentsAndContingenciesTables" xlink:href="ucbi-20190930.xsd#CommitmentsAndContingenciesTables" xlink:type="simple" />
  <link:roleRef roleURI="http://ucbi.com/role/CommonStock" xlink:href="ucbi-20190930.xsd#CommonStock" xlink:type="simple" />
  <link:roleRef roleURI="http://ucbi.com/role/CommonStockDetails" xlink:href="ucbi-20190930.xsd#CommonStockDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://ucbi.com/role/ConsolidatedBalanceSheetsUnaudited" xlink:href="ucbi-20190930.xsd#ConsolidatedBalanceSheetsUnaudited" xlink:type="simple" />
  <link:roleRef roleURI="http://ucbi.com/role/ConsolidatedBalanceSheetsUnauditedParentheticals" xlink:href="ucbi-20190930.xsd#ConsolidatedBalanceSheetsUnauditedParentheticals" xlink:type="simple" />
  <link:roleRef roleURI="http://ucbi.com/role/ConsolidatedStatementOfChangesInShareholdersEquityUnaudited" xlink:href="ucbi-20190930.xsd#ConsolidatedStatementOfChangesInShareholdersEquityUnaudited" xlink:type="simple" />
  <link:roleRef roleURI="http://ucbi.com/role/ConsolidatedStatementOfChangesInShareholdersEquityUnauditedParentheticals" xlink:href="ucbi-20190930.xsd#ConsolidatedStatementOfChangesInShareholdersEquityUnauditedParentheticals" xlink:type="simple" />
  <link:roleRef roleURI="http://ucbi.com/role/ConsolidatedStatementsOfCashFlowsUnaudited" xlink:href="ucbi-20190930.xsd#ConsolidatedStatementsOfCashFlowsUnaudited" xlink:type="simple" />
  <link:roleRef roleURI="http://ucbi.com/role/ConsolidatedStatementsOfComprehensiveIncomeUnaudited" xlink:href="ucbi-20190930.xsd#ConsolidatedStatementsOfComprehensiveIncomeUnaudited" xlink:type="simple" />
  <link:roleRef roleURI="http://ucbi.com/role/ConsolidatedStatementsOfIncomeUnaudited" xlink:href="ucbi-20190930.xsd#ConsolidatedStatementsOfIncomeUnaudited" xlink:type="simple" />
  <link:roleRef roleURI="http://ucbi.com/role/ConsolidatedStatementsOfIncomeUnauditedParentheticals" xlink:href="ucbi-20190930.xsd#ConsolidatedStatementsOfIncomeUnauditedParentheticals" xlink:type="simple" />
  <link:roleRef roleURI="http://ucbi.com/role/CoverPage" xlink:href="ucbi-20190930.xsd#CoverPage" xlink:type="simple" />
  <link:roleRef roleURI="http://ucbi.com/role/DerivativesAndHedgingActivities" xlink:href="ucbi-20190930.xsd#DerivativesAndHedgingActivities" xlink:type="simple" />
  <link:roleRef roleURI="http://ucbi.com/role/DerivativesAndHedgingActivitiesDerivativesDesignatedAsHedgingInstrumentsDetails" xlink:href="ucbi-20190930.xsd#DerivativesAndHedgingActivitiesDerivativesDesignatedAsHedgingInstrumentsDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://ucbi.com/role/DerivativesAndHedgingActivitiesDerivativesInFairValueHedgingRelationshipsDetails" xlink:href="ucbi-20190930.xsd#DerivativesAndHedgingActivitiesDerivativesInFairValueHedgingRelationshipsDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://ucbi.com/role/DerivativesAndHedgingActivitiesDerivativesNotDesignatedAsHedgingInstrumentsDetails" xlink:href="ucbi-20190930.xsd#DerivativesAndHedgingActivitiesDerivativesNotDesignatedAsHedgingInstrumentsDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://ucbi.com/role/DerivativesAndHedgingActivitiesGainsAndLossesRecognizedInIncomeOnDerivativesNotDesignatedAsHedgingInstrumentsDetails" xlink:href="ucbi-20190930.xsd#DerivativesAndHedgingActivitiesGainsAndLossesRecognizedInIncomeOnDerivativesNotDesignatedAsHedgingInstrumentsDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://ucbi.com/role/DerivativesAndHedgingActivitiesNarrativeDetails" xlink:href="ucbi-20190930.xsd#DerivativesAndHedgingActivitiesNarrativeDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://ucbi.com/role/DerivativesAndHedgingActivitiesTables" xlink:href="ucbi-20190930.xsd#DerivativesAndHedgingActivitiesTables" xlink:type="simple" />
  <link:roleRef roleURI="http://ucbi.com/role/EarningsPerShare" xlink:href="ucbi-20190930.xsd#EarningsPerShare" xlink:type="simple" />
  <link:roleRef roleURI="http://ucbi.com/role/EarningsPerShareComputationOfBasicAndDilutedEarningsPerShareDetails" xlink:href="ucbi-20190930.xsd#EarningsPerShareComputationOfBasicAndDilutedEarningsPerShareDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://ucbi.com/role/EarningsPerShareNarrativeDetails" xlink:href="ucbi-20190930.xsd#EarningsPerShareNarrativeDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://ucbi.com/role/EarningsPerShareTables" xlink:href="ucbi-20190930.xsd#EarningsPerShareTables" xlink:type="simple" />
  <link:roleRef roleURI="http://ucbi.com/role/GoodwillAndOtherIntangibleAssets" xlink:href="ucbi-20190930.xsd#GoodwillAndOtherIntangibleAssets" xlink:type="simple" />
  <link:roleRef roleURI="http://ucbi.com/role/GoodwillAndOtherIntangibleAssetsCarryingAmountDetails" xlink:href="ucbi-20190930.xsd#GoodwillAndOtherIntangibleAssetsCarryingAmountDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://ucbi.com/role/GoodwillAndOtherIntangibleAssetsChangesInCarryingAmountOfGoodwillDetails" xlink:href="ucbi-20190930.xsd#GoodwillAndOtherIntangibleAssetsChangesInCarryingAmountOfGoodwillDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://ucbi.com/role/GoodwillAndOtherIntangibleAssetsEstimatedAggregateAmortizationExpenseForFuturePeriodsDetails" xlink:href="ucbi-20190930.xsd#GoodwillAndOtherIntangibleAssetsEstimatedAggregateAmortizationExpenseForFuturePeriodsDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://ucbi.com/role/GoodwillAndOtherIntangibleAssetsTables" xlink:href="ucbi-20190930.xsd#GoodwillAndOtherIntangibleAssetsTables" xlink:type="simple" />
  <link:roleRef roleURI="http://ucbi.com/role/IncomeTaxes" xlink:href="ucbi-20190930.xsd#IncomeTaxes" xlink:type="simple" />
  <link:roleRef roleURI="http://ucbi.com/role/IncomeTaxesNarrativeDetails" xlink:href="ucbi-20190930.xsd#IncomeTaxesNarrativeDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://ucbi.com/role/LoansAndLeasesAndAllowanceForCreditLosses" xlink:href="ucbi-20190930.xsd#LoansAndLeasesAndAllowanceForCreditLosses" xlink:type="simple" />
  <link:roleRef roleURI="http://ucbi.com/role/LoansAndLeasesAndAllowanceForCreditLossesAgingOfRecordedInvestmentInPastDueLoansDetails" xlink:href="ucbi-20190930.xsd#LoansAndLeasesAndAllowanceForCreditLossesAgingOfRecordedInvestmentInPastDueLoansDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://ucbi.com/role/LoansAndLeasesAndAllowanceForCreditLossesAverageBalancesOfImpairedLoansAndIncomeRecognizedOnImpairedLoansDetails" xlink:href="ucbi-20190930.xsd#LoansAndLeasesAndAllowanceForCreditLossesAverageBalancesOfImpairedLoansAndIncomeRecognizedOnImpairedLoansDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://ucbi.com/role/LoansAndLeasesAndAllowanceForCreditLossesBalanceAndActivityInAllowanceForLoanLossesByPortfolioSegmentAndRecordedInvestmentInLoansByPortfolioSegmentDetails" xlink:href="ucbi-20190930.xsd#LoansAndLeasesAndAllowanceForCreditLossesBalanceAndActivityInAllowanceForLoanLossesByPortfolioSegmentAndRecordedInvestmentInLoansByPortfolioSegmentDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://ucbi.com/role/LoansAndLeasesAndAllowanceForCreditLossesChangesInValueOfAccretableYieldForAcquiredLoansDetails" xlink:href="ucbi-20190930.xsd#LoansAndLeasesAndAllowanceForCreditLossesChangesInValueOfAccretableYieldForAcquiredLoansDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://ucbi.com/role/LoansAndLeasesAndAllowanceForCreditLossesComponentsOfNetInvestmentInLeasesDetails" xlink:href="ucbi-20190930.xsd#LoansAndLeasesAndAllowanceForCreditLossesComponentsOfNetInvestmentInLeasesDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://ucbi.com/role/LoansAndLeasesAndAllowanceForCreditLossesLoansIndividuallyEvaluatedForImpairmentByClassOfLoansDetails" xlink:href="ucbi-20190930.xsd#LoansAndLeasesAndAllowanceForCreditLossesLoansIndividuallyEvaluatedForImpairmentByClassOfLoansDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://ucbi.com/role/LoansAndLeasesAndAllowanceForCreditLossesLoansModifiedUnderTermsOfTdrDetails" xlink:href="ucbi-20190930.xsd#LoansAndLeasesAndAllowanceForCreditLossesLoansModifiedUnderTermsOfTdrDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://ucbi.com/role/LoansAndLeasesAndAllowanceForCreditLossesMajorClassificationsOfLoansDetails" xlink:href="ucbi-20190930.xsd#LoansAndLeasesAndAllowanceForCreditLossesMajorClassificationsOfLoansDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://ucbi.com/role/LoansAndLeasesAndAllowanceForCreditLossesMinimumFutureLeasePaymentToBeReceivedDetails" xlink:href="ucbi-20190930.xsd#LoansAndLeasesAndAllowanceForCreditLossesMinimumFutureLeasePaymentToBeReceivedDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://ucbi.com/role/LoansAndLeasesAndAllowanceForCreditLossesNarrativeDetails" xlink:href="ucbi-20190930.xsd#LoansAndLeasesAndAllowanceForCreditLossesNarrativeDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://ucbi.com/role/LoansAndLeasesAndAllowanceForCreditLossesRecordedInvestmentInLoansByPortfolioSegmentAndBalanceOfAllowanceForLoanLossesDetails" xlink:href="ucbi-20190930.xsd#LoansAndLeasesAndAllowanceForCreditLossesRecordedInvestmentInLoansByPortfolioSegmentAndBalanceOfAllowanceForLoanLossesDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://ucbi.com/role/LoansAndLeasesAndAllowanceForCreditLossesRecordedInvestmentInNonaccrualLoansByLoanClassDetails" xlink:href="ucbi-20190930.xsd#LoansAndLeasesAndAllowanceForCreditLossesRecordedInvestmentInNonaccrualLoansByLoanClassDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://ucbi.com/role/LoansAndLeasesAndAllowanceForCreditLossesRiskCategoryOfLoansByClassOfLoansDetails" xlink:href="ucbi-20190930.xsd#LoansAndLeasesAndAllowanceForCreditLossesRiskCategoryOfLoansByClassOfLoansDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://ucbi.com/role/LoansAndLeasesAndAllowanceForCreditLossesTables" xlink:href="ucbi-20190930.xsd#LoansAndLeasesAndAllowanceForCreditLossesTables" xlink:type="simple" />
  <link:roleRef roleURI="http://ucbi.com/role/OperatingLeases" xlink:href="ucbi-20190930.xsd#OperatingLeases" xlink:type="simple" />
  <link:roleRef roleURI="http://ucbi.com/role/OperatingLeasesFutureMinimumLeasePaymentsDetails" xlink:href="ucbi-20190930.xsd#OperatingLeasesFutureMinimumLeasePaymentsDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://ucbi.com/role/OperatingLeasesNarrativeDetails" xlink:href="ucbi-20190930.xsd#OperatingLeasesNarrativeDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://ucbi.com/role/OperatingLeasesOperatingLeaseIncomeAndExpenseAndOtherSupplementalInformationDetails" xlink:href="ucbi-20190930.xsd#OperatingLeasesOperatingLeaseIncomeAndExpenseAndOtherSupplementalInformationDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://ucbi.com/role/OperatingLeasesTables" xlink:href="ucbi-20190930.xsd#OperatingLeasesTables" xlink:type="simple" />
  <link:roleRef roleURI="http://ucbi.com/role/ReclassificationsOutOfAccumulatedOtherComprehensiveIncome" xlink:href="ucbi-20190930.xsd#ReclassificationsOutOfAccumulatedOtherComprehensiveIncome" xlink:type="simple" />
  <link:roleRef roleURI="http://ucbi.com/role/ReclassificationsOutOfAccumulatedOtherComprehensiveIncomeDetails" xlink:href="ucbi-20190930.xsd#ReclassificationsOutOfAccumulatedOtherComprehensiveIncomeDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://ucbi.com/role/ReclassificationsOutOfAccumulatedOtherComprehensiveIncomeTables" xlink:href="ucbi-20190930.xsd#ReclassificationsOutOfAccumulatedOtherComprehensiveIncomeTables" xlink:type="simple" />
  <link:roleRef roleURI="http://ucbi.com/role/Securities" xlink:href="ucbi-20190930.xsd#Securities" xlink:type="simple" />
  <link:roleRef roleURI="http://ucbi.com/role/SecuritiesAmortizedCostAndFairValueOfHeldToMaturityAndAvailableForSaleSecuritiesByContractualMaturityDetails" xlink:href="ucbi-20190930.xsd#SecuritiesAmortizedCostAndFairValueOfHeldToMaturityAndAvailableForSaleSecuritiesByContractualMaturityDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://ucbi.com/role/SecuritiesAmortizedCostGrossUnrealizedGainsAndLossesAndFairValueOfDebtSecuritiesAvailableForSaleDetails" xlink:href="ucbi-20190930.xsd#SecuritiesAmortizedCostGrossUnrealizedGainsAndLossesAndFairValueOfDebtSecuritiesAvailableForSaleDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://ucbi.com/role/SecuritiesAmortizedCostGrossUnrealizedGainsAndLossesAndFairValueOfDebtSecuritiesHeldToMaturityDetails" xlink:href="ucbi-20190930.xsd#SecuritiesAmortizedCostGrossUnrealizedGainsAndLossesAndFairValueOfDebtSecuritiesHeldToMaturityDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://ucbi.com/role/SecuritiesNarrativeDetails" xlink:href="ucbi-20190930.xsd#SecuritiesNarrativeDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://ucbi.com/role/SecuritiesSummaryOfAvailableForSaleSecuritiesSalesActivityDetails" xlink:href="ucbi-20190930.xsd#SecuritiesSummaryOfAvailableForSaleSecuritiesSalesActivityDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://ucbi.com/role/SecuritiesSummaryOfDebtSecuritesHeldToMaturityInUnrealizedLossPositionDetails" xlink:href="ucbi-20190930.xsd#SecuritiesSummaryOfDebtSecuritesHeldToMaturityInUnrealizedLossPositionDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://ucbi.com/role/SecuritiesSummaryOfDebtSecuritiesAvailableForSaleInUnrealizedLossPositionDetails" xlink:href="ucbi-20190930.xsd#SecuritiesSummaryOfDebtSecuritiesAvailableForSaleInUnrealizedLossPositionDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://ucbi.com/role/SecuritiesTables" xlink:href="ucbi-20190930.xsd#SecuritiesTables" xlink:type="simple" />
  <link:roleRef roleURI="http://ucbi.com/role/StockBasedCompensation" xlink:href="ucbi-20190930.xsd#StockBasedCompensation" xlink:type="simple" />
  <link:roleRef roleURI="http://ucbi.com/role/StockBasedCompensationNarrativeDetails" xlink:href="ucbi-20190930.xsd#StockBasedCompensationNarrativeDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://ucbi.com/role/StockBasedCompensationRestrictedStockUnitActivityDetails" xlink:href="ucbi-20190930.xsd#StockBasedCompensationRestrictedStockUnitActivityDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://ucbi.com/role/StockBasedCompensationStockOptionActivityDetails" xlink:href="ucbi-20190930.xsd#StockBasedCompensationStockOptionActivityDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://ucbi.com/role/StockBasedCompensationTables" xlink:href="ucbi-20190930.xsd#StockBasedCompensationTables" xlink:type="simple" />
  <link:roleRef roleURI="http://ucbi.com/role/SubsequentEvents" xlink:href="ucbi-20190930.xsd#SubsequentEvents" xlink:type="simple" />
  <link:roleRef roleURI="http://ucbi.com/role/SubsequentEventsNarrativeDetails" xlink:href="ucbi-20190930.xsd#SubsequentEventsNarrativeDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://ucbi.com/role/TerminationOfDefinedBenefitPlanDetails" xlink:href="ucbi-20190930.xsd#TerminationOfDefinedBenefitPlanDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://ucbi.com/role/TerminationOfDefinedBenefitPlanNotes" xlink:href="ucbi-20190930.xsd#TerminationOfDefinedBenefitPlanNotes" xlink:type="simple" />
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/all" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#all" xlink:type="simple" />
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-default" xlink:type="simple" />
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-domain" xlink:type="simple" />
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/domain-member" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#domain-member" xlink:type="simple" />
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#hypercube-dimension" xlink:type="simple" />
  <link:definitionLink xlink:role="http://ucbi.com/role/AccountingPolicies" xlink:type="extended" />
  <link:definitionLink xlink:role="http://ucbi.com/role/AccountingPoliciesPolicies" xlink:type="extended" />
  <link:definitionLink xlink:role="http://ucbi.com/role/AccountingStandardsUpdatesAndRecentlyAdoptedStandards" xlink:type="extended" />
  <link:definitionLink xlink:role="http://ucbi.com/role/AccountingStandardsUpdatesAndRecentlyAdoptedStandardsNarrativeDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems" xlink:label="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems_DC6DD47433C15670B412D339E6551102" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleTable" xlink:label="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleTable_38E4DBD5C8A95DDBBB426674CF711CB4" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems_DC6DD47433C15670B412D339E6551102" xlink:to="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleTable_38E4DBD5C8A95DDBBB426674CF711CB4" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AdjustmentsForNewAccountingPronouncementsAxis" xlink:label="loc_us-gaap_AdjustmentsForNewAccountingPronouncementsAxis_7F3ED2F43DCD589BA3A4FA290822C911" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleTable_38E4DBD5C8A95DDBBB426674CF711CB4" xlink:to="loc_us-gaap_AdjustmentsForNewAccountingPronouncementsAxis_7F3ED2F43DCD589BA3A4FA290822C911" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_TypeOfAdoptionMember" xlink:label="loc_us-gaap_TypeOfAdoptionMember_8AFD1E21900495DFEB09F747E2E0FB44_3639CE68F660501A8F4042849B1BEF0D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AdjustmentsForNewAccountingPronouncementsAxis_7F3ED2F43DCD589BA3A4FA290822C911" xlink:to="loc_us-gaap_TypeOfAdoptionMember_8AFD1E21900495DFEB09F747E2E0FB44_3639CE68F660501A8F4042849B1BEF0D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_TypeOfAdoptionMember" xlink:label="loc_us-gaap_TypeOfAdoptionMember_5EA808D98CF5587BAC60626C14221D65" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AdjustmentsForNewAccountingPronouncementsAxis_7F3ED2F43DCD589BA3A4FA290822C911" xlink:to="loc_us-gaap_TypeOfAdoptionMember_5EA808D98CF5587BAC60626C14221D65" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AccountingStandardsUpdate201602Member" xlink:label="loc_us-gaap_AccountingStandardsUpdate201602Member_18171F1DF4DF562381E341647AF31705" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TypeOfAdoptionMember_5EA808D98CF5587BAC60626C14221D65" xlink:to="loc_us-gaap_AccountingStandardsUpdate201602Member_18171F1DF4DF562381E341647AF31705" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OperatingLeaseRightOfUseAsset" xlink:label="loc_us-gaap_OperatingLeaseRightOfUseAsset_F97EE602029D5086BDEC1954E2A1EFA4" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems_DC6DD47433C15670B412D339E6551102" xlink:to="loc_us-gaap_OperatingLeaseRightOfUseAsset_F97EE602029D5086BDEC1954E2A1EFA4" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OperatingLeaseLiability" xlink:label="loc_us-gaap_OperatingLeaseLiability_6779591639FB5986A68A346230E85FC9" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems_DC6DD47433C15670B412D339E6551102" xlink:to="loc_us-gaap_OperatingLeaseLiability_6779591639FB5986A68A346230E85FC9" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption" xlink:label="loc_us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption_CF04A1D26AE65370AB73D2953663FEF0" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems_DC6DD47433C15670B412D339E6551102" xlink:to="loc_us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption_CF04A1D26AE65370AB73D2953663FEF0" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://ucbi.com/role/Acquisitions" xlink:type="extended" />
  <link:definitionLink xlink:role="http://ucbi.com/role/AcquisitionsAcquiredLoanAndLeasePortfolioAtAcquisitionDateDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessAcquisitionLineItems" xlink:label="loc_us-gaap_BusinessAcquisitionLineItems_15E1B6E5ACE852FC93FE45AED7A99721" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable" xlink:label="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_95454905ED9C5B8E8629CC111EFBC2CA" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_15E1B6E5ACE852FC93FE45AED7A99721" xlink:to="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_95454905ED9C5B8E8629CC111EFBC2CA" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessAcquisitionAxis" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_3037DAD2E982508796BFA45A344E9B11" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_95454905ED9C5B8E8629CC111EFBC2CA" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_3037DAD2E982508796BFA45A344E9B11" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_DD9AC72437B120C9CC0F5D69B4B5AF28_3639CE68F660501A8F4042849B1BEF0D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_3037DAD2E982508796BFA45A344E9B11" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_DD9AC72437B120C9CC0F5D69B4B5AF28_3639CE68F660501A8F4042849B1BEF0D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_3F938892E99450D59CB5DA29E89F444A" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_3037DAD2E982508796BFA45A344E9B11" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_3F938892E99450D59CB5DA29E89F444A" xlink:type="arc" />
    <link:loc xlink:href="ucbi-20190930.xsd#ucbi_FirstMadisonAcquisitionMember" xlink:label="loc_ucbi_FirstMadisonAcquisitionMember_7705F055281552429AF5EFA3F57A423D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_3F938892E99450D59CB5DA29E89F444A" xlink:to="loc_ucbi_FirstMadisonAcquisitionMember_7705F055281552429AF5EFA3F57A423D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CertainLoansAcquiredInTransferAccountedForAsHeldToMaturityDebtSecuritiesAcquiredDuringPeriodAbstract" xlink:label="loc_us-gaap_CertainLoansAcquiredInTransferAccountedForAsHeldToMaturityDebtSecuritiesAcquiredDuringPeriodAbstract_A57C9681561D5258B09DE37C91E11674" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_15E1B6E5ACE852FC93FE45AED7A99721" xlink:to="loc_us-gaap_CertainLoansAcquiredInTransferAccountedForAsHeldToMaturityDebtSecuritiesAcquiredDuringPeriodAbstract_A57C9681561D5258B09DE37C91E11674" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CertainLoansAcquiredInTransferAccountedForAsHeldToMaturityDebtSecuritiesAcquiredDuringPeriodContractuallyRequiredPaymentsReceivableAtAcquisition" xlink:label="loc_us-gaap_CertainLoansAcquiredInTransferAccountedForAsHeldToMaturityDebtSecuritiesAcquiredDuringPeriodContractuallyRequiredPaymentsReceivableAtAcquisition_F9DCFC1574DC5CB389D4AD44BD9CEEE7" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CertainLoansAcquiredInTransferAccountedForAsHeldToMaturityDebtSecuritiesAcquiredDuringPeriodAbstract_A57C9681561D5258B09DE37C91E11674" xlink:to="loc_us-gaap_CertainLoansAcquiredInTransferAccountedForAsHeldToMaturityDebtSecuritiesAcquiredDuringPeriodContractuallyRequiredPaymentsReceivableAtAcquisition_F9DCFC1574DC5CB389D4AD44BD9CEEE7" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CertainLoansAcquiredInTransferNonaccretableDifference" xlink:label="loc_us-gaap_CertainLoansAcquiredInTransferNonaccretableDifference_D5879A5DE0645D289886717FFE2CDD9A" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CertainLoansAcquiredInTransferAccountedForAsHeldToMaturityDebtSecuritiesAcquiredDuringPeriodAbstract_A57C9681561D5258B09DE37C91E11674" xlink:to="loc_us-gaap_CertainLoansAcquiredInTransferNonaccretableDifference_D5879A5DE0645D289886717FFE2CDD9A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CertainLoansAcquiredInTransferAccountedForAsHeldToMaturityDebtSecuritiesAcquiredDuringPeriodCashFlowsExpectedToBeCollectedAtAcquisition" xlink:label="loc_us-gaap_CertainLoansAcquiredInTransferAccountedForAsHeldToMaturityDebtSecuritiesAcquiredDuringPeriodCashFlowsExpectedToBeCollectedAtAcquisition_3559371604B85488BFD9327BB8922BF1" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CertainLoansAcquiredInTransferAccountedForAsHeldToMaturityDebtSecuritiesAcquiredDuringPeriodAbstract_A57C9681561D5258B09DE37C91E11674" xlink:to="loc_us-gaap_CertainLoansAcquiredInTransferAccountedForAsHeldToMaturityDebtSecuritiesAcquiredDuringPeriodCashFlowsExpectedToBeCollectedAtAcquisition_3559371604B85488BFD9327BB8922BF1" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CertainLoansAcquiredInTransferAccretableYield" xlink:label="loc_us-gaap_CertainLoansAcquiredInTransferAccretableYield_B2A5D49A2B435F5F8D5A7B11AD2E8968" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CertainLoansAcquiredInTransferAccountedForAsHeldToMaturityDebtSecuritiesAcquiredDuringPeriodAbstract_A57C9681561D5258B09DE37C91E11674" xlink:to="loc_us-gaap_CertainLoansAcquiredInTransferAccretableYield_B2A5D49A2B435F5F8D5A7B11AD2E8968" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CertainLoansAcquiredInTransferAccountedForAsHeldToMaturityDebtSecuritiesAcquiredDuringPeriodAtAcquisitionAtFairValue" xlink:label="loc_us-gaap_CertainLoansAcquiredInTransferAccountedForAsHeldToMaturityDebtSecuritiesAcquiredDuringPeriodAtAcquisitionAtFairValue_AAE97472D4A954C390068D19EAA4DB06" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CertainLoansAcquiredInTransferAccountedForAsHeldToMaturityDebtSecuritiesAcquiredDuringPeriodAbstract_A57C9681561D5258B09DE37C91E11674" xlink:to="loc_us-gaap_CertainLoansAcquiredInTransferAccountedForAsHeldToMaturityDebtSecuritiesAcquiredDuringPeriodAtAcquisitionAtFairValue_AAE97472D4A954C390068D19EAA4DB06" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessCombinationAcquiredReceivablesAbstract" xlink:label="loc_us-gaap_BusinessCombinationAcquiredReceivablesAbstract_C802C79D276B54B18B9CA498D9AD1723" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_15E1B6E5ACE852FC93FE45AED7A99721" xlink:to="loc_us-gaap_BusinessCombinationAcquiredReceivablesAbstract_C802C79D276B54B18B9CA498D9AD1723" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessCombinationAcquiredReceivablesFairValue" xlink:label="loc_us-gaap_BusinessCombinationAcquiredReceivablesFairValue_582BC6F6DD5C589989829293574F0667" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationAcquiredReceivablesAbstract_C802C79D276B54B18B9CA498D9AD1723" xlink:to="loc_us-gaap_BusinessCombinationAcquiredReceivablesFairValue_582BC6F6DD5C589989829293574F0667" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessCombinationAcquiredReceivablesGrossContractualAmount" xlink:label="loc_us-gaap_BusinessCombinationAcquiredReceivablesGrossContractualAmount_354F2ABDF87A56818496348618926F66" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationAcquiredReceivablesAbstract_C802C79D276B54B18B9CA498D9AD1723" xlink:to="loc_us-gaap_BusinessCombinationAcquiredReceivablesGrossContractualAmount_354F2ABDF87A56818496348618926F66" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessCombinationAcquiredReceivablesEstimatedUncollectible" xlink:label="loc_us-gaap_BusinessCombinationAcquiredReceivablesEstimatedUncollectible_B053BBC6E869512B894D448DE689A5D3" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationAcquiredReceivablesAbstract_C802C79D276B54B18B9CA498D9AD1723" xlink:to="loc_us-gaap_BusinessCombinationAcquiredReceivablesEstimatedUncollectible_B053BBC6E869512B894D448DE689A5D3" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://ucbi.com/role/AcquisitionsAcquisitionDateFairValueOfPurchasedAssetsAndLiabilitiesDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessAcquisitionLineItems" xlink:label="loc_us-gaap_BusinessAcquisitionLineItems_3DDD43E31AE656C08E5232A05DE059A0" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable" xlink:label="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_3A18A82E7389595D866AE38F9F808394" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_3DDD43E31AE656C08E5232A05DE059A0" xlink:to="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_3A18A82E7389595D866AE38F9F808394" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessAcquisitionAxis" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_5BF98672271B5A88BEBB2048E2328907" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_3A18A82E7389595D866AE38F9F808394" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_5BF98672271B5A88BEBB2048E2328907" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_98B42382748F8918BB3E722178426666_3639CE68F660501A8F4042849B1BEF0D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_5BF98672271B5A88BEBB2048E2328907" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_98B42382748F8918BB3E722178426666_3639CE68F660501A8F4042849B1BEF0D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_47653C202BEB5BF490126E311B4ECCCC" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_5BF98672271B5A88BEBB2048E2328907" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_47653C202BEB5BF490126E311B4ECCCC" xlink:type="arc" />
    <link:loc xlink:href="ucbi-20190930.xsd#ucbi_FirstMadisonAcquisitionMember" xlink:label="loc_ucbi_FirstMadisonAcquisitionMember_424CEF0D143B5ABBA4ABB73FBEBA37AD" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_47653C202BEB5BF490126E311B4ECCCC" xlink:to="loc_ucbi_FirstMadisonAcquisitionMember_424CEF0D143B5ABBA4ABB73FBEBA37AD" xlink:type="arc" />
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_LegalEntityAxis" xlink:label="loc_dei_LegalEntityAxis_C204A05623DB54A68764233CFE401A61" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_3A18A82E7389595D866AE38F9F808394" xlink:to="loc_dei_LegalEntityAxis_C204A05623DB54A68764233CFE401A61" xlink:type="arc" />
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_EntityDomain" xlink:label="loc_dei_EntityDomain_194EF86BDBC2AB9C4CC3722178435F69_3639CE68F660501A8F4042849B1BEF0D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_C204A05623DB54A68764233CFE401A61" xlink:to="loc_dei_EntityDomain_194EF86BDBC2AB9C4CC3722178435F69_3639CE68F660501A8F4042849B1BEF0D" xlink:type="arc" />
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_EntityDomain" xlink:label="loc_dei_EntityDomain_991AD3A3735B5C39B8A0471158EBC89B" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_C204A05623DB54A68764233CFE401A61" xlink:to="loc_dei_EntityDomain_991AD3A3735B5C39B8A0471158EBC89B" xlink:type="arc" />
    <link:loc xlink:href="ucbi-20190930.xsd#ucbi_FirstMadisonBankAndTrustMember" xlink:label="loc_ucbi_FirstMadisonBankAndTrustMember_633C71DA641F5E77A38329E496196FA3" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_991AD3A3735B5C39B8A0471158EBC89B" xlink:to="loc_ucbi_FirstMadisonBankAndTrustMember_633C71DA641F5E77A38329E496196FA3" xlink:type="arc" />
    <link:loc xlink:href="ucbi-20190930.xsd#ucbi_FairValueOfPurchasedAssetsAndAssumedLiabilitiesRecordedAxis" xlink:label="loc_ucbi_FairValueOfPurchasedAssetsAndAssumedLiabilitiesRecordedAxis_4C55019C3B195676A9593D646C4C39BB" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_3A18A82E7389595D866AE38F9F808394" xlink:to="loc_ucbi_FairValueOfPurchasedAssetsAndAssumedLiabilitiesRecordedAxis_4C55019C3B195676A9593D646C4C39BB" xlink:type="arc" />
    <link:loc xlink:href="ucbi-20190930.xsd#ucbi_FairValueOfPurchasedAssetsAndAssumedLiabilitiesRecordedDomain" xlink:label="loc_ucbi_FairValueOfPurchasedAssetsAndAssumedLiabilitiesRecordedDomain_6690E6884E647BDDDE7D72217844D239_3639CE68F660501A8F4042849B1BEF0D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_ucbi_FairValueOfPurchasedAssetsAndAssumedLiabilitiesRecordedAxis_4C55019C3B195676A9593D646C4C39BB" xlink:to="loc_ucbi_FairValueOfPurchasedAssetsAndAssumedLiabilitiesRecordedDomain_6690E6884E647BDDDE7D72217844D239_3639CE68F660501A8F4042849B1BEF0D" xlink:type="arc" />
    <link:loc xlink:href="ucbi-20190930.xsd#ucbi_FairValueOfPurchasedAssetsAndAssumedLiabilitiesRecordedDomain" xlink:label="loc_ucbi_FairValueOfPurchasedAssetsAndAssumedLiabilitiesRecordedDomain_9D644689D3A55BC2A08BC9CA71C02E31" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_ucbi_FairValueOfPurchasedAssetsAndAssumedLiabilitiesRecordedAxis_4C55019C3B195676A9593D646C4C39BB" xlink:to="loc_ucbi_FairValueOfPurchasedAssetsAndAssumedLiabilitiesRecordedDomain_9D644689D3A55BC2A08BC9CA71C02E31" xlink:type="arc" />
    <link:loc xlink:href="ucbi-20190930.xsd#ucbi_AsRecordedByFirstMadisonBankAndTrustMember" xlink:label="loc_ucbi_AsRecordedByFirstMadisonBankAndTrustMember_90B01D9576CC55D5B38CE09BDD6C0A24" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ucbi_FairValueOfPurchasedAssetsAndAssumedLiabilitiesRecordedDomain_9D644689D3A55BC2A08BC9CA71C02E31" xlink:to="loc_ucbi_AsRecordedByFirstMadisonBankAndTrustMember_90B01D9576CC55D5B38CE09BDD6C0A24" xlink:type="arc" />
    <link:loc xlink:href="ucbi-20190930.xsd#ucbi_FairValueAdjustmentsAcquisitionMember" xlink:label="loc_ucbi_FairValueAdjustmentsAcquisitionMember_F108675B0EA15067B75EDBC470A9E60B" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ucbi_FairValueOfPurchasedAssetsAndAssumedLiabilitiesRecordedDomain_9D644689D3A55BC2A08BC9CA71C02E31" xlink:to="loc_ucbi_FairValueAdjustmentsAcquisitionMember_F108675B0EA15067B75EDBC470A9E60B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssetsAbstract" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssetsAbstract_830CFC2CD8C15ECCABD522E1CDE5FC53" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_3DDD43E31AE656C08E5232A05DE059A0" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssetsAbstract_830CFC2CD8C15ECCABD522E1CDE5FC53" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCashAndEquivalents" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCashAndEquivalents_BA8BF53469765A62BA8E61A635CEB3DB" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssetsAbstract_830CFC2CD8C15ECCABD522E1CDE5FC53" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCashAndEquivalents_BA8BF53469765A62BA8E61A635CEB3DB" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsReceivables" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsReceivables_040CC201C9635E518EB17C3173B86FDB" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssetsAbstract_830CFC2CD8C15ECCABD522E1CDE5FC53" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsReceivables_040CC201C9635E518EB17C3173B86FDB" xlink:type="arc" />
    <link:loc xlink:href="ucbi-20190930.xsd#ucbi_BusinessCombinationRecognizedIdentifiableAssetsAcquiredandLiabilitiesAssumedCurrentAssetsAllowanceForReceivables" xlink:label="loc_ucbi_BusinessCombinationRecognizedIdentifiableAssetsAcquiredandLiabilitiesAssumedCurrentAssetsAllowanceForReceivables_B45759C9EC595F1FAD2EA9009D874296" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssetsAbstract_830CFC2CD8C15ECCABD522E1CDE5FC53" xlink:to="loc_ucbi_BusinessCombinationRecognizedIdentifiableAssetsAcquiredandLiabilitiesAssumedCurrentAssetsAllowanceForReceivables_B45759C9EC595F1FAD2EA9009D874296" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedPropertyPlantAndEquipment" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedPropertyPlantAndEquipment_DD48799AB3DB562BAEEFB4275AE3063C" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssetsAbstract_830CFC2CD8C15ECCABD522E1CDE5FC53" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedPropertyPlantAndEquipment_DD48799AB3DB562BAEEFB4275AE3063C" xlink:type="arc" />
    <link:loc xlink:href="ucbi-20190930.xsd#ucbi_BusinessCombinationRecognizedIdentifiableAssetsAcquiredandLiabilitiesAssumedCurrentAssetsBankOwnedLifeInsurance" xlink:label="loc_ucbi_BusinessCombinationRecognizedIdentifiableAssetsAcquiredandLiabilitiesAssumedCurrentAssetsBankOwnedLifeInsurance_75E007EA933454A1B8C4A90F5499C795" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssetsAbstract_830CFC2CD8C15ECCABD522E1CDE5FC53" xlink:to="loc_ucbi_BusinessCombinationRecognizedIdentifiableAssetsAcquiredandLiabilitiesAssumedCurrentAssetsBankOwnedLifeInsurance_75E007EA933454A1B8C4A90F5499C795" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedDeferredTaxAssets" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedDeferredTaxAssets_ADBAD5BFF27C555E925BE844F608B0E8" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssetsAbstract_830CFC2CD8C15ECCABD522E1CDE5FC53" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedDeferredTaxAssets_ADBAD5BFF27C555E925BE844F608B0E8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibles" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibles_AB4FC5C3EFB652DF9CCD3A8D2DFFDD42" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssetsAbstract_830CFC2CD8C15ECCABD522E1CDE5FC53" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibles_AB4FC5C3EFB652DF9CCD3A8D2DFFDD42" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedOtherNoncurrentAssets" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedOtherNoncurrentAssets_9C9D98A9BB1A5AC9B9BB4819683E8661" xlink:type="locator" />
    <link:definitionArc order="8" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssetsAbstract_830CFC2CD8C15ECCABD522E1CDE5FC53" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedOtherNoncurrentAssets_9C9D98A9BB1A5AC9B9BB4819683E8661" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssets" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssets_F9E1B679811F5AA8BEE556A07259ED08" xlink:type="locator" />
    <link:definitionArc order="9" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssetsAbstract_830CFC2CD8C15ECCABD522E1CDE5FC53" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssets_F9E1B679811F5AA8BEE556A07259ED08" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLiabilitiesAbstract" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLiabilitiesAbstract_96DD8FF357535040867BD403917F7503" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_3DDD43E31AE656C08E5232A05DE059A0" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLiabilitiesAbstract_96DD8FF357535040867BD403917F7503" xlink:type="arc" />
    <link:loc xlink:href="ucbi-20190930.xsd#ucbi_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedDeposits" xlink:label="loc_ucbi_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedDeposits_DC8435741E26516184B377BD48F33B48" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLiabilitiesAbstract_96DD8FF357535040867BD403917F7503" xlink:to="loc_ucbi_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedDeposits_DC8435741E26516184B377BD48F33B48" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNoncurrentLiabilitiesOther" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNoncurrentLiabilitiesOther_BDC4886A821B5D84AB82A2D8725579E4" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLiabilitiesAbstract_96DD8FF357535040867BD403917F7503" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNoncurrentLiabilitiesOther_BDC4886A821B5D84AB82A2D8725579E4" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLiabilities" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLiabilities_09D3941ED2905BC9A3E27956F6F56B3D" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLiabilitiesAbstract_96DD8FF357535040867BD403917F7503" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLiabilities_09D3941ED2905BC9A3E27956F6F56B3D" xlink:type="arc" />
    <link:loc xlink:href="ucbi-20190930.xsd#ucbi_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedExcessOfAssetsAcquiredOverLiabilitiesAssumed" xlink:label="loc_ucbi_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedExcessOfAssetsAcquiredOverLiabilitiesAssumed_EE5C71620783536D920CDB09C478B2A8" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_3DDD43E31AE656C08E5232A05DE059A0" xlink:to="loc_ucbi_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedExcessOfAssetsAcquiredOverLiabilitiesAssumed_EE5C71620783536D920CDB09C478B2A8" xlink:type="arc" />
    <link:loc xlink:href="ucbi-20190930.xsd#ucbi_AggregateFairValueAdjustments" xlink:label="loc_ucbi_AggregateFairValueAdjustments_94534414320A53039C171876477D3B4E" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_3DDD43E31AE656C08E5232A05DE059A0" xlink:to="loc_ucbi_AggregateFairValueAdjustments_94534414320A53039C171876477D3B4E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNet" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNet_99450A0382565A2FB7D862C24323F842" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_3DDD43E31AE656C08E5232A05DE059A0" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNet_99450A0382565A2FB7D862C24323F842" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PaymentsToAcquireBusinessesGross" xlink:label="loc_us-gaap_PaymentsToAcquireBusinessesGross_688EDB5674C856E08396766E789B6A61" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_3DDD43E31AE656C08E5232A05DE059A0" xlink:to="loc_us-gaap_PaymentsToAcquireBusinessesGross_688EDB5674C856E08396766E789B6A61" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_Goodwill" xlink:label="loc_us-gaap_Goodwill_5D3FED5652E85C48A2BF486950CC3C5C" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_3DDD43E31AE656C08E5232A05DE059A0" xlink:to="loc_us-gaap_Goodwill_5D3FED5652E85C48A2BF486950CC3C5C" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://ucbi.com/role/AcquisitionsNarrativeDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessAcquisitionLineItems" xlink:label="loc_us-gaap_BusinessAcquisitionLineItems_17517A7E774865AD0B2F39D3E97BC50A" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable" xlink:label="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_F734C62F6E1CA70CCF4039D3E97817BA" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_17517A7E774865AD0B2F39D3E97BC50A" xlink:to="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_F734C62F6E1CA70CCF4039D3E97817BA" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_NonrecurringAdjustmentAxis" xlink:label="loc_us-gaap_NonrecurringAdjustmentAxis_453B67B3353CB922134D39D3E9792C16" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_F734C62F6E1CA70CCF4039D3E97817BA" xlink:to="loc_us-gaap_NonrecurringAdjustmentAxis_453B67B3353CB922134D39D3E9792C16" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_NonrecurringAdjustmentDomain" xlink:label="loc_us-gaap_NonrecurringAdjustmentDomain_35FA75AB5307614B13AC39D3E9792261_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_NonrecurringAdjustmentAxis_453B67B3353CB922134D39D3E9792C16" xlink:to="loc_us-gaap_NonrecurringAdjustmentDomain_35FA75AB5307614B13AC39D3E9792261_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_NonrecurringAdjustmentDomain" xlink:label="loc_us-gaap_NonrecurringAdjustmentDomain_35FA75AB5307614B13AC39D3E9792261" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_NonrecurringAdjustmentAxis_453B67B3353CB922134D39D3E9792C16" xlink:to="loc_us-gaap_NonrecurringAdjustmentDomain_35FA75AB5307614B13AC39D3E9792261" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AcquisitionRelatedCostsMember" xlink:label="loc_us-gaap_AcquisitionRelatedCostsMember_85167567C1BF538D3DB439D3E9794946" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NonrecurringAdjustmentDomain_35FA75AB5307614B13AC39D3E9792261" xlink:to="loc_us-gaap_AcquisitionRelatedCostsMember_85167567C1BF538D3DB439D3E9794946" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_65B8B9CD2099FD5D463D39D3E9792FC7" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_F734C62F6E1CA70CCF4039D3E97817BA" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_65B8B9CD2099FD5D463D39D3E9792FC7" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_46AEF9E2FDBAE6C8A59739D3E97A1656_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_65B8B9CD2099FD5D463D39D3E9792FC7" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_46AEF9E2FDBAE6C8A59739D3E97A1656_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_46AEF9E2FDBAE6C8A59739D3E97A1656" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_65B8B9CD2099FD5D463D39D3E9792FC7" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_46AEF9E2FDBAE6C8A59739D3E97A1656" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CoreDepositsMember" xlink:label="loc_us-gaap_CoreDepositsMember_7A9F0EF4E2BCDC9FC6FD39D3E97A9677" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_46AEF9E2FDBAE6C8A59739D3E97A1656" xlink:to="loc_us-gaap_CoreDepositsMember_7A9F0EF4E2BCDC9FC6FD39D3E97A9677" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessAcquisitionAxis" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_1D0FDC16751F142F1F9239D3E97A5CA9" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_F734C62F6E1CA70CCF4039D3E97817BA" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_1D0FDC16751F142F1F9239D3E97A5CA9" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_DB01718B4EB14963456B39D3E97A3B53_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_1D0FDC16751F142F1F9239D3E97A5CA9" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_DB01718B4EB14963456B39D3E97A3B53_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_DB01718B4EB14963456B39D3E97A3B53" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_1D0FDC16751F142F1F9239D3E97A5CA9" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_DB01718B4EB14963456B39D3E97A3B53" xlink:type="arc" />
    <link:loc xlink:href="ucbi-20190930.xsd#ucbi_FirstMadisonAcquisitionMember" xlink:label="loc_ucbi_FirstMadisonAcquisitionMember_73BFE99DAD4CD628E42E39D3E97A9C5F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_DB01718B4EB14963456B39D3E97A3B53" xlink:to="loc_ucbi_FirstMadisonAcquisitionMember_73BFE99DAD4CD628E42E39D3E97A9C5F" xlink:type="arc" />
    <link:loc xlink:href="ucbi-20190930.xsd#ucbi_NLFCHoldingsCorpAcquisitionMember" xlink:label="loc_ucbi_NLFCHoldingsCorpAcquisitionMember_B00E9A488CEE9D2F717439D3E97BA9F5" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_DB01718B4EB14963456B39D3E97A3B53" xlink:to="loc_ucbi_NLFCHoldingsCorpAcquisitionMember_B00E9A488CEE9D2F717439D3E97BA9F5" xlink:type="arc" />
    <link:loc xlink:href="ucbi-20190930.xsd#ucbi_NumberOfBranches" xlink:label="loc_ucbi_NumberOfBranches_175B5723CE945BBE58A139D3E97BC3C5" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_17517A7E774865AD0B2F39D3E97BC50A" xlink:to="loc_ucbi_NumberOfBranches_175B5723CE945BBE58A139D3E97BC3C5" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssets" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssets_74181BAAB2ECBFC5A6B339D3E97B031C" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_17517A7E774865AD0B2F39D3E97BC50A" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssets_74181BAAB2ECBFC5A6B339D3E97B031C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLiabilities" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLiabilities_073A58E7D02A363452C239D3E97C0D87" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_17517A7E774865AD0B2F39D3E97BC50A" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLiabilities_073A58E7D02A363452C239D3E97C0D87" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PaymentsToAcquireBusinessesGross" xlink:label="loc_us-gaap_PaymentsToAcquireBusinessesGross_BC5F8C79DF76F6B5A56039D3E97C507A" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_17517A7E774865AD0B2F39D3E97BC50A" xlink:to="loc_us-gaap_PaymentsToAcquireBusinessesGross_BC5F8C79DF76F6B5A56039D3E97C507A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_Goodwill" xlink:label="loc_us-gaap_Goodwill_B405313E0CE752195EEF39D3E97C9E50" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_17517A7E774865AD0B2F39D3E97BC50A" xlink:to="loc_us-gaap_Goodwill_B405313E0CE752195EEF39D3E97C9E50" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessAcquisitionPurchasePriceAllocationGoodwillExpectedTaxDeductibleAmount" xlink:label="loc_us-gaap_BusinessAcquisitionPurchasePriceAllocationGoodwillExpectedTaxDeductibleAmount_D75B4764C9250EEF82A139D3E97C8021" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_17517A7E774865AD0B2F39D3E97BC50A" xlink:to="loc_us-gaap_BusinessAcquisitionPurchasePriceAllocationGoodwillExpectedTaxDeductibleAmount_D75B4764C9250EEF82A139D3E97C8021" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibles" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibles_3114269C12129AA87A6039D3E97C3F50" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_17517A7E774865AD0B2F39D3E97BC50A" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibles_3114269C12129AA87A6039D3E97C3F50" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AcquiredFiniteLivedIntangibleAssetsWeightedAverageUsefulLife" xlink:label="loc_us-gaap_AcquiredFiniteLivedIntangibleAssetsWeightedAverageUsefulLife_9956D1C00D6E9F80D14839D3E97CEAA0" xlink:type="locator" />
    <link:definitionArc order="8" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_17517A7E774865AD0B2F39D3E97BC50A" xlink:to="loc_us-gaap_AcquiredFiniteLivedIntangibleAssetsWeightedAverageUsefulLife_9956D1C00D6E9F80D14839D3E97CEAA0" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessCombinationAcquisitionRelatedCosts" xlink:label="loc_us-gaap_BusinessCombinationAcquisitionRelatedCosts_A26A92E673B2B2A7675D39D3E97D7EA5" xlink:type="locator" />
    <link:definitionArc order="9" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_17517A7E774865AD0B2F39D3E97BC50A" xlink:to="loc_us-gaap_BusinessCombinationAcquisitionRelatedCosts_A26A92E673B2B2A7675D39D3E97D7EA5" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://ucbi.com/role/AcquisitionsProFormaInformationDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessAcquisitionLineItems" xlink:label="loc_us-gaap_BusinessAcquisitionLineItems_01ECC855D04D5CD899B4370B6A9E8439" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable" xlink:label="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_172B325CD466541F8573377B483841C5" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_01ECC855D04D5CD899B4370B6A9E8439" xlink:to="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_172B325CD466541F8573377B483841C5" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessAcquisitionAxis" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_80F79E615139513DA6BE683EFE033429" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_172B325CD466541F8573377B483841C5" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_80F79E615139513DA6BE683EFE033429" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_D5D9AC7DCD2FA73AC9AF5D69B4B3A84B_3639CE68F660501A8F4042849B1BEF0D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_80F79E615139513DA6BE683EFE033429" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_D5D9AC7DCD2FA73AC9AF5D69B4B3A84B_3639CE68F660501A8F4042849B1BEF0D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_1A69F778930155A7ADC49669CEBDDB56" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_80F79E615139513DA6BE683EFE033429" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_1A69F778930155A7ADC49669CEBDDB56" xlink:type="arc" />
    <link:loc xlink:href="ucbi-20190930.xsd#ucbi_FirstMadisonAcquisitionMember" xlink:label="loc_ucbi_FirstMadisonAcquisitionMember_05506D24A8055652A4FE9E2914AD1866" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_1A69F778930155A7ADC49669CEBDDB56" xlink:to="loc_ucbi_FirstMadisonAcquisitionMember_05506D24A8055652A4FE9E2914AD1866" xlink:type="arc" />
    <link:loc xlink:href="ucbi-20190930.xsd#ucbi_NLFCHoldingsCorpAcquisitionMember" xlink:label="loc_ucbi_NLFCHoldingsCorpAcquisitionMember_3DB9093A892850F8ABBCF228FA74683E" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_1A69F778930155A7ADC49669CEBDDB56" xlink:to="loc_ucbi_NLFCHoldingsCorpAcquisitionMember_3DB9093A892850F8ABBCF228FA74683E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessCombinationProFormaInformationRevenueOfAcquireeSinceAcquisitionDateActual" xlink:label="loc_us-gaap_BusinessCombinationProFormaInformationRevenueOfAcquireeSinceAcquisitionDateActual_0EF544B3CA7D56D0A2D42CCA261E4D3A" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_01ECC855D04D5CD899B4370B6A9E8439" xlink:to="loc_us-gaap_BusinessCombinationProFormaInformationRevenueOfAcquireeSinceAcquisitionDateActual_0EF544B3CA7D56D0A2D42CCA261E4D3A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessCombinationProFormaInformationEarningsOrLossOfAcquireeSinceAcquisitionDateActual" xlink:label="loc_us-gaap_BusinessCombinationProFormaInformationEarningsOrLossOfAcquireeSinceAcquisitionDateActual_E36C185D8D5F547ABD4018AF3359C0D8" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_01ECC855D04D5CD899B4370B6A9E8439" xlink:to="loc_us-gaap_BusinessCombinationProFormaInformationEarningsOrLossOfAcquireeSinceAcquisitionDateActual_E36C185D8D5F547ABD4018AF3359C0D8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessAcquisitionsProFormaRevenue" xlink:label="loc_us-gaap_BusinessAcquisitionsProFormaRevenue_B10C1FD94B83540CB60B85EC6D8CDCB4" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_01ECC855D04D5CD899B4370B6A9E8439" xlink:to="loc_us-gaap_BusinessAcquisitionsProFormaRevenue_B10C1FD94B83540CB60B85EC6D8CDCB4" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessAcquisitionsProFormaNetIncomeLoss" xlink:label="loc_us-gaap_BusinessAcquisitionsProFormaNetIncomeLoss_2E905E52C332503488EDA3D8496F62A7" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_01ECC855D04D5CD899B4370B6A9E8439" xlink:to="loc_us-gaap_BusinessAcquisitionsProFormaNetIncomeLoss_2E905E52C332503488EDA3D8496F62A7" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://ucbi.com/role/AcquisitionsTables" xlink:type="extended" />
  <link:definitionLink xlink:role="http://ucbi.com/role/AssetsAndLiabilitiesMeasuredAtFairValue" xlink:type="extended" />
  <link:definitionLink xlink:role="http://ucbi.com/role/AssetsAndLiabilitiesMeasuredAtFairValueAssetsAndLiabilitiesMeasuredAtFairValueOnNonrecurringBasisDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_C23C02AFB4F8507B89EEB14BDC2F9F92" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_37CFCB64B2AD526D89DE60E8E58B8AC2" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_C23C02AFB4F8507B89EEB14BDC2F9F92" xlink:to="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_37CFCB64B2AD526D89DE60E8E58B8AC2" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueByMeasurementFrequencyAxis" xlink:label="loc_us-gaap_FairValueByMeasurementFrequencyAxis_EE9FC7055F0753C6BBBCBFCC75605BB8" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_37CFCB64B2AD526D89DE60E8E58B8AC2" xlink:to="loc_us-gaap_FairValueByMeasurementFrequencyAxis_EE9FC7055F0753C6BBBCBFCC75605BB8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueMeasurementFrequencyDomain" xlink:label="loc_us-gaap_FairValueMeasurementFrequencyDomain_E47E743A608DCD420027F747E348F1D1_3639CE68F660501A8F4042849B1BEF0D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByMeasurementFrequencyAxis_EE9FC7055F0753C6BBBCBFCC75605BB8" xlink:to="loc_us-gaap_FairValueMeasurementFrequencyDomain_E47E743A608DCD420027F747E348F1D1_3639CE68F660501A8F4042849B1BEF0D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueMeasurementFrequencyDomain" xlink:label="loc_us-gaap_FairValueMeasurementFrequencyDomain_2DC4D561E9855109B0575768718B10DD" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByMeasurementFrequencyAxis_EE9FC7055F0753C6BBBCBFCC75605BB8" xlink:to="loc_us-gaap_FairValueMeasurementFrequencyDomain_2DC4D561E9855109B0575768718B10DD" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueMeasurementsNonrecurringMember" xlink:label="loc_us-gaap_FairValueMeasurementsNonrecurringMember_E2915875BEDB59B2A748FF6A155C6BBF" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementFrequencyDomain_2DC4D561E9855109B0575768718B10DD" xlink:to="loc_us-gaap_FairValueMeasurementsNonrecurringMember_E2915875BEDB59B2A748FF6A155C6BBF" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis" xlink:label="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_031E60C37C3A553AA2FE79075DB87131" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_37CFCB64B2AD526D89DE60E8E58B8AC2" xlink:to="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_031E60C37C3A553AA2FE79075DB87131" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_3E4E371C4E9E1A6ED29DF747E3493554_3639CE68F660501A8F4042849B1BEF0D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_031E60C37C3A553AA2FE79075DB87131" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_3E4E371C4E9E1A6ED29DF747E3493554_3639CE68F660501A8F4042849B1BEF0D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_378221D2897553A5A5B494EF72DA4AB8" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_031E60C37C3A553AA2FE79075DB87131" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_378221D2897553A5A5B494EF72DA4AB8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueInputsLevel1Member" xlink:label="loc_us-gaap_FairValueInputsLevel1Member_C874E5B408C759EB8255488EB973A8AE" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_378221D2897553A5A5B494EF72DA4AB8" xlink:to="loc_us-gaap_FairValueInputsLevel1Member_C874E5B408C759EB8255488EB973A8AE" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueInputsLevel2Member" xlink:label="loc_us-gaap_FairValueInputsLevel2Member_D344024EC19553BC8BD3B1F161FDF9C3" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_378221D2897553A5A5B494EF72DA4AB8" xlink:to="loc_us-gaap_FairValueInputsLevel2Member_D344024EC19553BC8BD3B1F161FDF9C3" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueInputsLevel3Member" xlink:label="loc_us-gaap_FairValueInputsLevel3Member_468E57A1CFBA57579E531850B19D5A6E" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_378221D2897553A5A5B494EF72DA4AB8" xlink:to="loc_us-gaap_FairValueInputsLevel3Member_468E57A1CFBA57579E531850B19D5A6E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AssetsFairValueDisclosure" xlink:label="loc_us-gaap_AssetsFairValueDisclosure_EAAE2385C82A528C8D9A4F8D813133A1" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_C23C02AFB4F8507B89EEB14BDC2F9F92" xlink:to="loc_us-gaap_AssetsFairValueDisclosure_EAAE2385C82A528C8D9A4F8D813133A1" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://ucbi.com/role/AssetsAndLiabilitiesMeasuredAtFairValueAssetsAndLiabilitiesMeasuredAtFairValueOnRecurringBasisDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_44A8D1C1D5A28D46E95147556BDE4100" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_5896614947FEA53E51F347556BD7AC22" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_44A8D1C1D5A28D46E95147556BDE4100" xlink:to="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_5896614947FEA53E51F347556BD7AC22" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueByMeasurementFrequencyAxis" xlink:label="loc_us-gaap_FairValueByMeasurementFrequencyAxis_5174E1FFBEFBECE7485947556BD89D90" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_5896614947FEA53E51F347556BD7AC22" xlink:to="loc_us-gaap_FairValueByMeasurementFrequencyAxis_5174E1FFBEFBECE7485947556BD89D90" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueMeasurementFrequencyDomain" xlink:label="loc_us-gaap_FairValueMeasurementFrequencyDomain_AFB9B5F46508317EA2E247556BD8F6ED_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByMeasurementFrequencyAxis_5174E1FFBEFBECE7485947556BD89D90" xlink:to="loc_us-gaap_FairValueMeasurementFrequencyDomain_AFB9B5F46508317EA2E247556BD8F6ED_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueMeasurementFrequencyDomain" xlink:label="loc_us-gaap_FairValueMeasurementFrequencyDomain_AFB9B5F46508317EA2E247556BD8F6ED" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByMeasurementFrequencyAxis_5174E1FFBEFBECE7485947556BD89D90" xlink:to="loc_us-gaap_FairValueMeasurementFrequencyDomain_AFB9B5F46508317EA2E247556BD8F6ED" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueMeasurementsRecurringMember" xlink:label="loc_us-gaap_FairValueMeasurementsRecurringMember_AFCB3F2DD8CF83129EDE47556BD98671" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementFrequencyDomain_AFB9B5F46508317EA2E247556BD8F6ED" xlink:to="loc_us-gaap_FairValueMeasurementsRecurringMember_AFCB3F2DD8CF83129EDE47556BD98671" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis" xlink:label="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_E0CEA55D8B33C96943F647556BD969A7" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_5896614947FEA53E51F347556BD7AC22" xlink:to="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_E0CEA55D8B33C96943F647556BD969A7" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_7D25D4C307C6F36B574347556BD9BB31_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_E0CEA55D8B33C96943F647556BD969A7" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_7D25D4C307C6F36B574347556BD9BB31_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_7D25D4C307C6F36B574347556BD9BB31" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_E0CEA55D8B33C96943F647556BD969A7" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_7D25D4C307C6F36B574347556BD9BB31" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueInputsLevel1Member" xlink:label="loc_us-gaap_FairValueInputsLevel1Member_529EE5166C2BBA50CAF447556BDA9EA4" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_7D25D4C307C6F36B574347556BD9BB31" xlink:to="loc_us-gaap_FairValueInputsLevel1Member_529EE5166C2BBA50CAF447556BDA9EA4" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueInputsLevel2Member" xlink:label="loc_us-gaap_FairValueInputsLevel2Member_DF7CC58ACDF30FC8E3FD47556BDC5ED6" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_7D25D4C307C6F36B574347556BD9BB31" xlink:to="loc_us-gaap_FairValueInputsLevel2Member_DF7CC58ACDF30FC8E3FD47556BDC5ED6" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueInputsLevel3Member" xlink:label="loc_us-gaap_FairValueInputsLevel3Member_894C5B81E0812A72888E47556BDC86FF" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_7D25D4C307C6F36B574347556BD9BB31" xlink:to="loc_us-gaap_FairValueInputsLevel3Member_894C5B81E0812A72888E47556BDC86FF" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FinancialInstrumentAxis" xlink:label="loc_us-gaap_FinancialInstrumentAxis_3FA7F458995EA4DB1A6447556BDCFECE" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_5896614947FEA53E51F347556BD7AC22" xlink:to="loc_us-gaap_FinancialInstrumentAxis_3FA7F458995EA4DB1A6447556BDCFECE" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_AC67BD1AB361420AE7FE47556BDC50DC_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_3FA7F458995EA4DB1A6447556BDCFECE" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_AC67BD1AB361420AE7FE47556BDC50DC_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_AC67BD1AB361420AE7FE47556BDC50DC" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_3FA7F458995EA4DB1A6447556BDCFECE" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_AC67BD1AB361420AE7FE47556BDC50DC" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_USTreasurySecuritiesMember" xlink:label="loc_us-gaap_USTreasurySecuritiesMember_D353A495C358FB2836D947556BDCB25D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_AC67BD1AB361420AE7FE47556BDC50DC" xlink:to="loc_us-gaap_USTreasurySecuritiesMember_D353A495C358FB2836D947556BDCB25D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_USTreasuryAndGovernmentMember" xlink:label="loc_us-gaap_USTreasuryAndGovernmentMember_54F0EA7EB432E884E5A247556BDD743B" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_AC67BD1AB361420AE7FE47556BDC50DC" xlink:to="loc_us-gaap_USTreasuryAndGovernmentMember_54F0EA7EB432E884E5A247556BDD743B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_USStatesAndPoliticalSubdivisionsMember" xlink:label="loc_us-gaap_USStatesAndPoliticalSubdivisionsMember_336363F4B3640740065B47556BDD9118" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_AC67BD1AB361420AE7FE47556BDC50DC" xlink:to="loc_us-gaap_USStatesAndPoliticalSubdivisionsMember_336363F4B3640740065B47556BDD9118" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ResidentialMortgageBackedSecuritiesMember" xlink:label="loc_us-gaap_ResidentialMortgageBackedSecuritiesMember_A46F2F1FD7F77B2C532947556BDD5DBB" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_AC67BD1AB361420AE7FE47556BDC50DC" xlink:to="loc_us-gaap_ResidentialMortgageBackedSecuritiesMember_A46F2F1FD7F77B2C532947556BDD5DBB" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CommercialMortgageBackedSecuritiesMember" xlink:label="loc_us-gaap_CommercialMortgageBackedSecuritiesMember_0C8E6A99450052728E9747556BDDDAA4" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_AC67BD1AB361420AE7FE47556BDC50DC" xlink:to="loc_us-gaap_CommercialMortgageBackedSecuritiesMember_0C8E6A99450052728E9747556BDDDAA4" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CorporateDebtSecuritiesMember" xlink:label="loc_us-gaap_CorporateDebtSecuritiesMember_00B65A9D477B34784CBC47556BDDBDE1" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_AC67BD1AB361420AE7FE47556BDC50DC" xlink:to="loc_us-gaap_CorporateDebtSecuritiesMember_00B65A9D477B34784CBC47556BDDBDE1" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AssetBackedSecuritiesMember" xlink:label="loc_us-gaap_AssetBackedSecuritiesMember_053B951B8C3EF3536A1047556BDD4554" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_AC67BD1AB361420AE7FE47556BDC50DC" xlink:to="loc_us-gaap_AssetBackedSecuritiesMember_053B951B8C3EF3536A1047556BDD4554" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_EquitySecuritiesMember" xlink:label="loc_us-gaap_EquitySecuritiesMember_B1254752E517B8C2C18847556BDE3E11" xlink:type="locator" />
    <link:definitionArc order="8" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_AC67BD1AB361420AE7FE47556BDC50DC" xlink:to="loc_us-gaap_EquitySecuritiesMember_B1254752E517B8C2C18847556BDE3E11" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AssetsFairValueDisclosureAbstract" xlink:label="loc_us-gaap_AssetsFairValueDisclosureAbstract_6EA8F016B1D8978AAE2747556BDEE8C8" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_44A8D1C1D5A28D46E95147556BDE4100" xlink:to="loc_us-gaap_AssetsFairValueDisclosureAbstract_6EA8F016B1D8978AAE2747556BDEE8C8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AvailableForSaleSecuritiesDebtSecurities" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtSecurities_47D29CD8EAF2F45E339447556BDE94E4" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsFairValueDisclosureAbstract_6EA8F016B1D8978AAE2747556BDEE8C8" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtSecurities_47D29CD8EAF2F45E339447556BDE94E4" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_MortgagesHeldForSaleFairValueDisclosure" xlink:label="loc_us-gaap_MortgagesHeldForSaleFairValueDisclosure_693DCECB76BB38805E3247556BDF92E8" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsFairValueDisclosureAbstract_6EA8F016B1D8978AAE2747556BDEE8C8" xlink:to="loc_us-gaap_MortgagesHeldForSaleFairValueDisclosure_693DCECB76BB38805E3247556BDF92E8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DeferredCompensationPlanAssets" xlink:label="loc_us-gaap_DeferredCompensationPlanAssets_3201243576374982A9F547556BDFDD02" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsFairValueDisclosureAbstract_6EA8F016B1D8978AAE2747556BDEE8C8" xlink:to="loc_us-gaap_DeferredCompensationPlanAssets_3201243576374982A9F547556BDFDD02" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ServicingAssetAtFairValueAmount" xlink:label="loc_us-gaap_ServicingAssetAtFairValueAmount_0F93380A380F079FE09F47556BE20224" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsFairValueDisclosureAbstract_6EA8F016B1D8978AAE2747556BDEE8C8" xlink:to="loc_us-gaap_ServicingAssetAtFairValueAmount_0F93380A380F079FE09F47556BE20224" xlink:type="arc" />
    <link:loc xlink:href="ucbi-20190930.xsd#ucbi_ResidentialMortgageServicingAssetatFairValueAmount" xlink:label="loc_ucbi_ResidentialMortgageServicingAssetatFairValueAmount_B73E4B74E124D88F2D5147556BE2941D" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsFairValueDisclosureAbstract_6EA8F016B1D8978AAE2747556BDEE8C8" xlink:to="loc_ucbi_ResidentialMortgageServicingAssetatFairValueAmount_B73E4B74E124D88F2D5147556BE2941D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DerivativeAssets" xlink:label="loc_us-gaap_DerivativeAssets_4587E62236F23F7745A647556BE30831" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsFairValueDisclosureAbstract_6EA8F016B1D8978AAE2747556BDEE8C8" xlink:to="loc_us-gaap_DerivativeAssets_4587E62236F23F7745A647556BE30831" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AssetsFairValueDisclosure" xlink:label="loc_us-gaap_AssetsFairValueDisclosure_4E76DEAC2672348F119747556BE38875" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsFairValueDisclosureAbstract_6EA8F016B1D8978AAE2747556BDEE8C8" xlink:to="loc_us-gaap_AssetsFairValueDisclosure_4E76DEAC2672348F119747556BE38875" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LiabilitiesFairValueDisclosureAbstract" xlink:label="loc_us-gaap_LiabilitiesFairValueDisclosureAbstract_93D217A632A0A455C0CC47556BE3F1D0" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_44A8D1C1D5A28D46E95147556BDE4100" xlink:to="loc_us-gaap_LiabilitiesFairValueDisclosureAbstract_93D217A632A0A455C0CC47556BE3F1D0" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DeferredCompensationLiabilityCurrentAndNoncurrent" xlink:label="loc_us-gaap_DeferredCompensationLiabilityCurrentAndNoncurrent_CDEB4D64A9A9A75B32394756F52F8338" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesFairValueDisclosureAbstract_93D217A632A0A455C0CC47556BE3F1D0" xlink:to="loc_us-gaap_DeferredCompensationLiabilityCurrentAndNoncurrent_CDEB4D64A9A9A75B32394756F52F8338" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DerivativeLiabilities" xlink:label="loc_us-gaap_DerivativeLiabilities_FDD32EB6A7ECFADCF73C47556BE34FD8" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesFairValueDisclosureAbstract_93D217A632A0A455C0CC47556BE3F1D0" xlink:to="loc_us-gaap_DerivativeLiabilities_FDD32EB6A7ECFADCF73C47556BE34FD8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LiabilitiesFairValueDisclosure" xlink:label="loc_us-gaap_LiabilitiesFairValueDisclosure_A57AD82AB742FA53289047556BE3F70C" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesFairValueDisclosureAbstract_93D217A632A0A455C0CC47556BE3F1D0" xlink:to="loc_us-gaap_LiabilitiesFairValueDisclosure_A57AD82AB742FA53289047556BE3F70C" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://ucbi.com/role/AssetsAndLiabilitiesMeasuredAtFairValueFairValuesForOtherFinancialInstrumentsThatAreNotMeasuredAtFairValueOnRecurringBasisDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_71AFAC35973255A58AE02F9EF79C6079" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_486A09AA9820576BAFD775AAC76A993C" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_71AFAC35973255A58AE02F9EF79C6079" xlink:to="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_486A09AA9820576BAFD775AAC76A993C" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueByMeasurementBasisAxis" xlink:label="loc_us-gaap_FairValueByMeasurementBasisAxis_F9EF8EDE672D5AC6B93692728845A319" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_486A09AA9820576BAFD775AAC76A993C" xlink:to="loc_us-gaap_FairValueByMeasurementBasisAxis_F9EF8EDE672D5AC6B93692728845A319" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PortionAtFairValueFairValueDisclosureMember" xlink:label="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_E54F75511211BB93072AF747E2BA49F1_3639CE68F660501A8F4042849B1BEF0D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByMeasurementBasisAxis_F9EF8EDE672D5AC6B93692728845A319" xlink:to="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_E54F75511211BB93072AF747E2BA49F1_3639CE68F660501A8F4042849B1BEF0D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueDisclosureItemAmountsDomain" xlink:label="loc_us-gaap_FairValueDisclosureItemAmountsDomain_150E6C49D273562AB8C1C4A3410C0EF0" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByMeasurementBasisAxis_F9EF8EDE672D5AC6B93692728845A319" xlink:to="loc_us-gaap_FairValueDisclosureItemAmountsDomain_150E6C49D273562AB8C1C4A3410C0EF0" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PortionAtFairValueFairValueDisclosureMember" xlink:label="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_A678737C10D954C0AD6FDD0317D6A248" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueDisclosureItemAmountsDomain_150E6C49D273562AB8C1C4A3410C0EF0" xlink:to="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_A678737C10D954C0AD6FDD0317D6A248" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CarryingReportedAmountFairValueDisclosureMember" xlink:label="loc_us-gaap_CarryingReportedAmountFairValueDisclosureMember_F169247EE14D55199FDE02C93434DFF7" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_A678737C10D954C0AD6FDD0317D6A248" xlink:to="loc_us-gaap_CarryingReportedAmountFairValueDisclosureMember_F169247EE14D55199FDE02C93434DFF7" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_EstimateOfFairValueFairValueDisclosureMember" xlink:label="loc_us-gaap_EstimateOfFairValueFairValueDisclosureMember_691454B9570F510ABC9B18458184312E" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_A678737C10D954C0AD6FDD0317D6A248" xlink:to="loc_us-gaap_EstimateOfFairValueFairValueDisclosureMember_691454B9570F510ABC9B18458184312E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis" xlink:label="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_38707FCCB7B35F49A0ED4127880517FA" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_486A09AA9820576BAFD775AAC76A993C" xlink:to="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_38707FCCB7B35F49A0ED4127880517FA" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_DF9C4948541711DAEAEDF747E2BB5C2F_3639CE68F660501A8F4042849B1BEF0D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_38707FCCB7B35F49A0ED4127880517FA" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_DF9C4948541711DAEAEDF747E2BB5C2F_3639CE68F660501A8F4042849B1BEF0D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_24775140D4CB535D99BB13A9984C0366" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_38707FCCB7B35F49A0ED4127880517FA" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_24775140D4CB535D99BB13A9984C0366" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueInputsLevel1Member" xlink:label="loc_us-gaap_FairValueInputsLevel1Member_88B98FE06769585A926DB9F88D0703A9" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_24775140D4CB535D99BB13A9984C0366" xlink:to="loc_us-gaap_FairValueInputsLevel1Member_88B98FE06769585A926DB9F88D0703A9" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueInputsLevel2Member" xlink:label="loc_us-gaap_FairValueInputsLevel2Member_D9428A38B31E52059969AB56BEB50F63" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_24775140D4CB535D99BB13A9984C0366" xlink:to="loc_us-gaap_FairValueInputsLevel2Member_D9428A38B31E52059969AB56BEB50F63" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueInputsLevel3Member" xlink:label="loc_us-gaap_FairValueInputsLevel3Member_5F366151E5B5565C9B09F4A4FCF2F0FB" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_24775140D4CB535D99BB13A9984C0366" xlink:to="loc_us-gaap_FairValueInputsLevel3Member_5F366151E5B5565C9B09F4A4FCF2F0FB" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FinancialInstrumentsFinancialAssetsBalanceSheetGroupingsAbstract" xlink:label="loc_us-gaap_FinancialInstrumentsFinancialAssetsBalanceSheetGroupingsAbstract_65DCBC7AF2AC528386AD3E79ED897435" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_71AFAC35973255A58AE02F9EF79C6079" xlink:to="loc_us-gaap_FinancialInstrumentsFinancialAssetsBalanceSheetGroupingsAbstract_65DCBC7AF2AC528386AD3E79ED897435" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_HeldToMaturitySecuritiesFairValue" xlink:label="loc_us-gaap_HeldToMaturitySecuritiesFairValue_E62852B66BB750ECBBDBBC00954F3FF8" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancialInstrumentsFinancialAssetsBalanceSheetGroupingsAbstract_65DCBC7AF2AC528386AD3E79ED897435" xlink:to="loc_us-gaap_HeldToMaturitySecuritiesFairValue_E62852B66BB750ECBBDBBC00954F3FF8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LoansReceivableFairValueDisclosure" xlink:label="loc_us-gaap_LoansReceivableFairValueDisclosure_3FD6E442785859CBB51859CAD3429A56" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancialInstrumentsFinancialAssetsBalanceSheetGroupingsAbstract_65DCBC7AF2AC528386AD3E79ED897435" xlink:to="loc_us-gaap_LoansReceivableFairValueDisclosure_3FD6E442785859CBB51859CAD3429A56" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FinancialInstrumentsFinancialLiabilitiesBalanceSheetGroupingsAbstract" xlink:label="loc_us-gaap_FinancialInstrumentsFinancialLiabilitiesBalanceSheetGroupingsAbstract_9D7AEB1AF847539CA132E185FF22BAEF" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_71AFAC35973255A58AE02F9EF79C6079" xlink:to="loc_us-gaap_FinancialInstrumentsFinancialLiabilitiesBalanceSheetGroupingsAbstract_9D7AEB1AF847539CA132E185FF22BAEF" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DepositsFairValueDisclosure" xlink:label="loc_us-gaap_DepositsFairValueDisclosure_558964B2E71D59D6B383EF46B9993A1A" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancialInstrumentsFinancialLiabilitiesBalanceSheetGroupingsAbstract_9D7AEB1AF847539CA132E185FF22BAEF" xlink:to="loc_us-gaap_DepositsFairValueDisclosure_558964B2E71D59D6B383EF46B9993A1A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FederalHomeLoanBankBorrowingsFairValueDisclosure" xlink:label="loc_us-gaap_FederalHomeLoanBankBorrowingsFairValueDisclosure_B9221E17F70353FBBDB5436E05098898" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancialInstrumentsFinancialLiabilitiesBalanceSheetGroupingsAbstract_9D7AEB1AF847539CA132E185FF22BAEF" xlink:to="loc_us-gaap_FederalHomeLoanBankBorrowingsFairValueDisclosure_B9221E17F70353FBBDB5436E05098898" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LongTermDebtFairValue" xlink:label="loc_us-gaap_LongTermDebtFairValue_0E28A23A82C351ACA00E640E0F5EA746" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancialInstrumentsFinancialLiabilitiesBalanceSheetGroupingsAbstract_9D7AEB1AF847539CA132E185FF22BAEF" xlink:to="loc_us-gaap_LongTermDebtFairValue_0E28A23A82C351ACA00E640E0F5EA746" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://ucbi.com/role/AssetsAndLiabilitiesMeasuredAtFairValueNarrativeDetails" xlink:type="extended" />
  <link:definitionLink xlink:role="http://ucbi.com/role/AssetsAndLiabilitiesMeasuredAtFairValueQuantitativeInformationAboutLevel3FairValueMeasurementsForFairValueOnRecurringBasisDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems_286EDE905D6A54558DCFD34B18BBB904" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable_1EE37FC543AB5E7694DEBD0C4BA70808" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems_286EDE905D6A54558DCFD34B18BBB904" xlink:to="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable_1EE37FC543AB5E7694DEBD0C4BA70808" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueByMeasurementFrequencyAxis" xlink:label="loc_us-gaap_FairValueByMeasurementFrequencyAxis_4FC5D72610075F9884A204DB1CE84531" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable_1EE37FC543AB5E7694DEBD0C4BA70808" xlink:to="loc_us-gaap_FairValueByMeasurementFrequencyAxis_4FC5D72610075F9884A204DB1CE84531" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueMeasurementFrequencyDomain" xlink:label="loc_us-gaap_FairValueMeasurementFrequencyDomain_0AC84C085E26A4F1DE8AF747E32019A8_3639CE68F660501A8F4042849B1BEF0D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByMeasurementFrequencyAxis_4FC5D72610075F9884A204DB1CE84531" xlink:to="loc_us-gaap_FairValueMeasurementFrequencyDomain_0AC84C085E26A4F1DE8AF747E32019A8_3639CE68F660501A8F4042849B1BEF0D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueMeasurementFrequencyDomain" xlink:label="loc_us-gaap_FairValueMeasurementFrequencyDomain_6EB0ECBF994E572A9CDCBBAC20DADADB" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByMeasurementFrequencyAxis_4FC5D72610075F9884A204DB1CE84531" xlink:to="loc_us-gaap_FairValueMeasurementFrequencyDomain_6EB0ECBF994E572A9CDCBBAC20DADADB" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueMeasurementsRecurringMember" xlink:label="loc_us-gaap_FairValueMeasurementsRecurringMember_3BC510B3B4A358B6B418A4D7C225FAAD" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementFrequencyDomain_6EB0ECBF994E572A9CDCBBAC20DADADB" xlink:to="loc_us-gaap_FairValueMeasurementsRecurringMember_3BC510B3B4A358B6B418A4D7C225FAAD" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis" xlink:label="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_6ACD06F2DEC75328A57D332B7F612909" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable_1EE37FC543AB5E7694DEBD0C4BA70808" xlink:to="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_6ACD06F2DEC75328A57D332B7F612909" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_BD1F737249BD4F3FBDFEF747E3219E1E_3639CE68F660501A8F4042849B1BEF0D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_6ACD06F2DEC75328A57D332B7F612909" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_BD1F737249BD4F3FBDFEF747E3219E1E_3639CE68F660501A8F4042849B1BEF0D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_026E033659385DC58C47D01F1397C7CD" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_6ACD06F2DEC75328A57D332B7F612909" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_026E033659385DC58C47D01F1397C7CD" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueInputsLevel3Member" xlink:label="loc_us-gaap_FairValueInputsLevel3Member_E9B7C5075515541B831E5EE2F96A6E3D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_026E033659385DC58C47D01F1397C7CD" xlink:to="loc_us-gaap_FairValueInputsLevel3Member_E9B7C5075515541B831E5EE2F96A6E3D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueByLiabilityClassAxis" xlink:label="loc_us-gaap_FairValueByLiabilityClassAxis_89819E84E1D0580E8F7DFE91F6590F98" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable_1EE37FC543AB5E7694DEBD0C4BA70808" xlink:to="loc_us-gaap_FairValueByLiabilityClassAxis_89819E84E1D0580E8F7DFE91F6590F98" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain" xlink:label="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_3667DBCC08AB5F55D378F747E321FC07_3639CE68F660501A8F4042849B1BEF0D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByLiabilityClassAxis_89819E84E1D0580E8F7DFE91F6590F98" xlink:to="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_3667DBCC08AB5F55D378F747E321FC07_3639CE68F660501A8F4042849B1BEF0D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain" xlink:label="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_A92A786AF12958D0811ABFB48A8FF5A1" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByLiabilityClassAxis_89819E84E1D0580E8F7DFE91F6590F98" xlink:to="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_A92A786AF12958D0811ABFB48A8FF5A1" xlink:type="arc" />
    <link:loc xlink:href="ucbi-20190930.xsd#ucbi_DerivativeLiabilitiesRiskParticipationsMember" xlink:label="loc_ucbi_DerivativeLiabilitiesRiskParticipationsMember_D22DD9BF4FEB5ACBA69AAABCD0DFEE10" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_A92A786AF12958D0811ABFB48A8FF5A1" xlink:to="loc_ucbi_DerivativeLiabilitiesRiskParticipationsMember_D22DD9BF4FEB5ACBA69AAABCD0DFEE10" xlink:type="arc" />
    <link:loc xlink:href="ucbi-20190930.xsd#ucbi_DerivativeLiabilityMember" xlink:label="loc_ucbi_DerivativeLiabilityMember_A901D17D0EC955209C139D73C9809984" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_A92A786AF12958D0811ABFB48A8FF5A1" xlink:to="loc_ucbi_DerivativeLiabilityMember_A901D17D0EC955209C139D73C9809984" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueByAssetClassAxis" xlink:label="loc_us-gaap_FairValueByAssetClassAxis_F2335F9E6EA55B8E9C31F1D7C1EFDBB7" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable_1EE37FC543AB5E7694DEBD0C4BA70808" xlink:to="loc_us-gaap_FairValueByAssetClassAxis_F2335F9E6EA55B8E9C31F1D7C1EFDBB7" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain" xlink:label="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_A90A6C0FAAB8EEBBB473F747E322AF74_3639CE68F660501A8F4042849B1BEF0D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByAssetClassAxis_F2335F9E6EA55B8E9C31F1D7C1EFDBB7" xlink:to="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_A90A6C0FAAB8EEBBB473F747E322AF74_3639CE68F660501A8F4042849B1BEF0D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain" xlink:label="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_40A93A901B265CF789F203501A7B370F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByAssetClassAxis_F2335F9E6EA55B8E9C31F1D7C1EFDBB7" xlink:to="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_40A93A901B265CF789F203501A7B370F" xlink:type="arc" />
    <link:loc xlink:href="ucbi-20190930.xsd#ucbi_SBAServicingRightsMember" xlink:label="loc_ucbi_SBAServicingRightsMember_06FEE67445A45AEEB63504B1D34E16A2" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_40A93A901B265CF789F203501A7B370F" xlink:to="loc_ucbi_SBAServicingRightsMember_06FEE67445A45AEEB63504B1D34E16A2" xlink:type="arc" />
    <link:loc xlink:href="ucbi-20190930.xsd#ucbi_ResidentialMortgageServicingRightsMember" xlink:label="loc_ucbi_ResidentialMortgageServicingRightsMember_A91ACE8A8F5A59A5BA5D9F60AFDE9669" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_40A93A901B265CF789F203501A7B370F" xlink:to="loc_ucbi_ResidentialMortgageServicingRightsMember_A91ACE8A8F5A59A5BA5D9F60AFDE9669" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CorporateDebtSecuritiesMember" xlink:label="loc_us-gaap_CorporateDebtSecuritiesMember_87BBB862EA305016AE1C2B280F7DF2A9" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_40A93A901B265CF789F203501A7B370F" xlink:to="loc_us-gaap_CorporateDebtSecuritiesMember_87BBB862EA305016AE1C2B280F7DF2A9" xlink:type="arc" />
    <link:loc xlink:href="ucbi-20190930.xsd#ucbi_DerivativeAssetMember" xlink:label="loc_ucbi_DerivativeAssetMember_D17E20DFADE5585F8B47519B86EA3B6C" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_40A93A901B265CF789F203501A7B370F" xlink:to="loc_ucbi_DerivativeAssetMember_D17E20DFADE5585F8B47519B86EA3B6C" xlink:type="arc" />
    <link:loc xlink:href="ucbi-20190930.xsd#ucbi_DerivativeAssetsOtherMember" xlink:label="loc_ucbi_DerivativeAssetsOtherMember_959580FBAC3E5718ADFEC4D4B18A9EAD" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_40A93A901B265CF789F203501A7B370F" xlink:to="loc_ucbi_DerivativeAssetsOtherMember_959580FBAC3E5718ADFEC4D4B18A9EAD" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_MeasurementInputTypeAxis" xlink:label="loc_us-gaap_MeasurementInputTypeAxis_C50C60FDC3F556B9A79DC6F20329E360" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable_1EE37FC543AB5E7694DEBD0C4BA70808" xlink:to="loc_us-gaap_MeasurementInputTypeAxis_C50C60FDC3F556B9A79DC6F20329E360" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_MeasurementInputTypeDomain" xlink:label="loc_us-gaap_MeasurementInputTypeDomain_90599E1DAEE3295DB12FF747E3240B90_3639CE68F660501A8F4042849B1BEF0D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_MeasurementInputTypeAxis_C50C60FDC3F556B9A79DC6F20329E360" xlink:to="loc_us-gaap_MeasurementInputTypeDomain_90599E1DAEE3295DB12FF747E3240B90_3639CE68F660501A8F4042849B1BEF0D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_MeasurementInputTypeDomain" xlink:label="loc_us-gaap_MeasurementInputTypeDomain_18B4A735591353E496D191B19081F97E" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_MeasurementInputTypeAxis_C50C60FDC3F556B9A79DC6F20329E360" xlink:to="loc_us-gaap_MeasurementInputTypeDomain_18B4A735591353E496D191B19081F97E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_MeasurementInputDiscountRateMember" xlink:label="loc_us-gaap_MeasurementInputDiscountRateMember_35F2F2C39B0758C59229F20D2B7945D8" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MeasurementInputTypeDomain_18B4A735591353E496D191B19081F97E" xlink:to="loc_us-gaap_MeasurementInputDiscountRateMember_35F2F2C39B0758C59229F20D2B7945D8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_MeasurementInputPrepaymentRateMember" xlink:label="loc_us-gaap_MeasurementInputPrepaymentRateMember_108FA0D7BE9D53D58C43B348DD4400CA" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MeasurementInputTypeDomain_18B4A735591353E496D191B19081F97E" xlink:to="loc_us-gaap_MeasurementInputPrepaymentRateMember_108FA0D7BE9D53D58C43B348DD4400CA" xlink:type="arc" />
    <link:loc xlink:href="ucbi-20190930.xsd#ucbi_MeasurementInputPullThroughRateMember" xlink:label="loc_ucbi_MeasurementInputPullThroughRateMember_764C83EE1B3D5CB2838647C04A3A580D" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MeasurementInputTypeDomain_18B4A735591353E496D191B19081F97E" xlink:to="loc_ucbi_MeasurementInputPullThroughRateMember_764C83EE1B3D5CB2838647C04A3A580D" xlink:type="arc" />
    <link:loc xlink:href="ucbi-20190930.xsd#ucbi_MeasurementInputProbableExposureRateMember" xlink:label="loc_ucbi_MeasurementInputProbableExposureRateMember_ACDF6F4A187F5FC991B4A9228105DCAF" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MeasurementInputTypeDomain_18B4A735591353E496D191B19081F97E" xlink:to="loc_ucbi_MeasurementInputProbableExposureRateMember_ACDF6F4A187F5FC991B4A9228105DCAF" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_MeasurementInputDefaultRateMember" xlink:label="loc_us-gaap_MeasurementInputDefaultRateMember_7496D2928607508782338DDB4FE681DF" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MeasurementInputTypeDomain_18B4A735591353E496D191B19081F97E" xlink:to="loc_us-gaap_MeasurementInputDefaultRateMember_7496D2928607508782338DDB4FE681DF" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_RangeAxis" xlink:label="loc_srt_RangeAxis_C191E300AE9758A3A93357C25F74BE9F" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable_1EE37FC543AB5E7694DEBD0C4BA70808" xlink:to="loc_srt_RangeAxis_C191E300AE9758A3A93357C25F74BE9F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_RangeMember" xlink:label="loc_srt_RangeMember_7E53FBAF1C7C936F94C0F747E3255022_3639CE68F660501A8F4042849B1BEF0D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_C191E300AE9758A3A93357C25F74BE9F" xlink:to="loc_srt_RangeMember_7E53FBAF1C7C936F94C0F747E3255022_3639CE68F660501A8F4042849B1BEF0D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_RangeMember" xlink:label="loc_srt_RangeMember_398054BB6B835102B00B113A70099B74" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_C191E300AE9758A3A93357C25F74BE9F" xlink:to="loc_srt_RangeMember_398054BB6B835102B00B113A70099B74" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_WeightedAverageMember" xlink:label="loc_srt_WeightedAverageMember_0A2AE2249F3B58098EDAAD78411E914D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_398054BB6B835102B00B113A70099B74" xlink:to="loc_srt_WeightedAverageMember_0A2AE2249F3B58098EDAAD78411E914D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ServicingAssetAtFairValueAmount" xlink:label="loc_us-gaap_ServicingAssetAtFairValueAmount_BF9D29B0F62659CCA9FF7673B0A7122C" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems_286EDE905D6A54558DCFD34B18BBB904" xlink:to="loc_us-gaap_ServicingAssetAtFairValueAmount_BF9D29B0F62659CCA9FF7673B0A7122C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ServicingAssetMeasurementInput" xlink:label="loc_us-gaap_ServicingAssetMeasurementInput_349ED66249E458CB920B436D7658EE60" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems_286EDE905D6A54558DCFD34B18BBB904" xlink:to="loc_us-gaap_ServicingAssetMeasurementInput_349ED66249E458CB920B436D7658EE60" xlink:type="arc" />
    <link:loc xlink:href="ucbi-20190930.xsd#ucbi_ResidentialMortgageServicingAssetatFairValueAmount" xlink:label="loc_ucbi_ResidentialMortgageServicingAssetatFairValueAmount_37F7CDA7234456EEBC656CE8CB72A4C0" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems_286EDE905D6A54558DCFD34B18BBB904" xlink:to="loc_ucbi_ResidentialMortgageServicingAssetatFairValueAmount_37F7CDA7234456EEBC656CE8CB72A4C0" xlink:type="arc" />
    <link:loc xlink:href="ucbi-20190930.xsd#ucbi_ResidentialMortgageServicingAssetMeasurementInput" xlink:label="loc_ucbi_ResidentialMortgageServicingAssetMeasurementInput_03726765C4945998AB0C3BE0126AB1D8" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems_286EDE905D6A54558DCFD34B18BBB904" xlink:to="loc_ucbi_ResidentialMortgageServicingAssetMeasurementInput_03726765C4945998AB0C3BE0126AB1D8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AvailableForSaleSecuritiesDebtSecurities" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtSecurities_8DCEF5E3743258F68A91D97D4F7968AB" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems_286EDE905D6A54558DCFD34B18BBB904" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtSecurities_8DCEF5E3743258F68A91D97D4F7968AB" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DerivativeAssets" xlink:label="loc_us-gaap_DerivativeAssets_AE6E5C09B15153ADB19D4AFC9860B7CD" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems_286EDE905D6A54558DCFD34B18BBB904" xlink:to="loc_us-gaap_DerivativeAssets_AE6E5C09B15153ADB19D4AFC9860B7CD" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DerivativeAssetMeasurementInput" xlink:label="loc_us-gaap_DerivativeAssetMeasurementInput_DC73240472D55FD6B743A3A260A40676" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems_286EDE905D6A54558DCFD34B18BBB904" xlink:to="loc_us-gaap_DerivativeAssetMeasurementInput_DC73240472D55FD6B743A3A260A40676" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DerivativeLiabilities" xlink:label="loc_us-gaap_DerivativeLiabilities_9F996B02556C561E823E2E7FB0D0F81F" xlink:type="locator" />
    <link:definitionArc order="8" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems_286EDE905D6A54558DCFD34B18BBB904" xlink:to="loc_us-gaap_DerivativeLiabilities_9F996B02556C561E823E2E7FB0D0F81F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DerivativeLiabilityMeasurementInput" xlink:label="loc_us-gaap_DerivativeLiabilityMeasurementInput_528C57C4E35856018EA7FC53171D4369" xlink:type="locator" />
    <link:definitionArc order="9" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems_286EDE905D6A54558DCFD34B18BBB904" xlink:to="loc_us-gaap_DerivativeLiabilityMeasurementInput_528C57C4E35856018EA7FC53171D4369" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueMeasurementsValuationProcessesDescription" xlink:label="loc_us-gaap_FairValueMeasurementsValuationProcessesDescription_B29A81CA0F9B5762B66A14F7EFC864C7" xlink:type="locator" />
    <link:definitionArc order="10" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems_286EDE905D6A54558DCFD34B18BBB904" xlink:to="loc_us-gaap_FairValueMeasurementsValuationProcessesDescription_B29A81CA0F9B5762B66A14F7EFC864C7" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://ucbi.com/role/AssetsAndLiabilitiesMeasuredAtFairValueReconciliationForMeasurementsAtFairValueOnRecurringBasisUsingSignificantUnobservableInputsDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems" xlink:label="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems_1427C51D9A405AAA892316E399413ADB" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_0A2D9F2BABB758AB8BCDC5630705F80A" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems_1427C51D9A405AAA892316E399413ADB" xlink:to="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_0A2D9F2BABB758AB8BCDC5630705F80A" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueByMeasurementFrequencyAxis" xlink:label="loc_us-gaap_FairValueByMeasurementFrequencyAxis_8C708F61A05D5340AC2B6E0288A483CF" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_0A2D9F2BABB758AB8BCDC5630705F80A" xlink:to="loc_us-gaap_FairValueByMeasurementFrequencyAxis_8C708F61A05D5340AC2B6E0288A483CF" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueMeasurementFrequencyDomain" xlink:label="loc_us-gaap_FairValueMeasurementFrequencyDomain_E285CA2CD2B230A1945E511E201A8EDF_3639CE68F660501A8F4042849B1BEF0D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByMeasurementFrequencyAxis_8C708F61A05D5340AC2B6E0288A483CF" xlink:to="loc_us-gaap_FairValueMeasurementFrequencyDomain_E285CA2CD2B230A1945E511E201A8EDF_3639CE68F660501A8F4042849B1BEF0D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueMeasurementFrequencyDomain" xlink:label="loc_us-gaap_FairValueMeasurementFrequencyDomain_64C0546E479A53CE872E7233C23E37B1" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByMeasurementFrequencyAxis_8C708F61A05D5340AC2B6E0288A483CF" xlink:to="loc_us-gaap_FairValueMeasurementFrequencyDomain_64C0546E479A53CE872E7233C23E37B1" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueMeasurementsRecurringMember" xlink:label="loc_us-gaap_FairValueMeasurementsRecurringMember_364788955D315EF89FB2CEC4A121DB25" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementFrequencyDomain_64C0546E479A53CE872E7233C23E37B1" xlink:to="loc_us-gaap_FairValueMeasurementsRecurringMember_364788955D315EF89FB2CEC4A121DB25" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis" xlink:label="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_3C3022AC2C675BDD983A330A97BFC560" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_0A2D9F2BABB758AB8BCDC5630705F80A" xlink:to="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_3C3022AC2C675BDD983A330A97BFC560" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_2B7551BB7F4F2A869582511E201A1E35_3639CE68F660501A8F4042849B1BEF0D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_3C3022AC2C675BDD983A330A97BFC560" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_2B7551BB7F4F2A869582511E201A1E35_3639CE68F660501A8F4042849B1BEF0D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_CD4E14B4590E502B8611A40D09724504" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_3C3022AC2C675BDD983A330A97BFC560" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_CD4E14B4590E502B8611A40D09724504" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueInputsLevel3Member" xlink:label="loc_us-gaap_FairValueInputsLevel3Member_2E951316FB6457F89E17A375B02D9931" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_CD4E14B4590E502B8611A40D09724504" xlink:to="loc_us-gaap_FairValueInputsLevel3Member_2E951316FB6457F89E17A375B02D9931" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueByLiabilityClassAxis" xlink:label="loc_us-gaap_FairValueByLiabilityClassAxis_81F3A530BE9A52D5ADB7FF4622113CC3" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_0A2D9F2BABB758AB8BCDC5630705F80A" xlink:to="loc_us-gaap_FairValueByLiabilityClassAxis_81F3A530BE9A52D5ADB7FF4622113CC3" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain" xlink:label="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_37DC7057D98DE98BF4CF511E201B1444_3639CE68F660501A8F4042849B1BEF0D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByLiabilityClassAxis_81F3A530BE9A52D5ADB7FF4622113CC3" xlink:to="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_37DC7057D98DE98BF4CF511E201B1444_3639CE68F660501A8F4042849B1BEF0D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain" xlink:label="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_946F27D35A9D5776B611BEE3E8758A4A" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByLiabilityClassAxis_81F3A530BE9A52D5ADB7FF4622113CC3" xlink:to="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_946F27D35A9D5776B611BEE3E8758A4A" xlink:type="arc" />
    <link:loc xlink:href="ucbi-20190930.xsd#ucbi_DerivativeLiabilityMember" xlink:label="loc_ucbi_DerivativeLiabilityMember_8B1C9CEC310357FABDCB1B6709EC6CC4" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_946F27D35A9D5776B611BEE3E8758A4A" xlink:to="loc_ucbi_DerivativeLiabilityMember_8B1C9CEC310357FABDCB1B6709EC6CC4" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueByAssetClassAxis" xlink:label="loc_us-gaap_FairValueByAssetClassAxis_252DEE498EB359AB9DEFF6DEFE88C742" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_0A2D9F2BABB758AB8BCDC5630705F80A" xlink:to="loc_us-gaap_FairValueByAssetClassAxis_252DEE498EB359AB9DEFF6DEFE88C742" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain" xlink:label="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_9CE993EDDD26DBD95F11511E201CB47D_3639CE68F660501A8F4042849B1BEF0D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByAssetClassAxis_252DEE498EB359AB9DEFF6DEFE88C742" xlink:to="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_9CE993EDDD26DBD95F11511E201CB47D_3639CE68F660501A8F4042849B1BEF0D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain" xlink:label="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_80BA7874C7ED50D681530CA20910DB5E" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByAssetClassAxis_252DEE498EB359AB9DEFF6DEFE88C742" xlink:to="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_80BA7874C7ED50D681530CA20910DB5E" xlink:type="arc" />
    <link:loc xlink:href="ucbi-20190930.xsd#ucbi_DerivativeAssetMember" xlink:label="loc_ucbi_DerivativeAssetMember_9E735D5D8BCB5703AA09AF06B2610B85" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_80BA7874C7ED50D681530CA20910DB5E" xlink:to="loc_ucbi_DerivativeAssetMember_9E735D5D8BCB5703AA09AF06B2610B85" xlink:type="arc" />
    <link:loc xlink:href="ucbi-20190930.xsd#ucbi_SBAServicingRightsMember" xlink:label="loc_ucbi_SBAServicingRightsMember_9AE9DE72F296504B9A59B3A9763CFC63" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_80BA7874C7ED50D681530CA20910DB5E" xlink:to="loc_ucbi_SBAServicingRightsMember_9AE9DE72F296504B9A59B3A9763CFC63" xlink:type="arc" />
    <link:loc xlink:href="ucbi-20190930.xsd#ucbi_ResidentialMortgageServicingRightsMember" xlink:label="loc_ucbi_ResidentialMortgageServicingRightsMember_19AC8716012A5D09BB7917EB8A124A80" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_80BA7874C7ED50D681530CA20910DB5E" xlink:to="loc_ucbi_ResidentialMortgageServicingRightsMember_19AC8716012A5D09BB7917EB8A124A80" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AvailableforsaleSecuritiesMember" xlink:label="loc_us-gaap_AvailableforsaleSecuritiesMember_579A07C84C9459BDAF544FF1AB8CCFFA" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_80BA7874C7ED50D681530CA20910DB5E" xlink:to="loc_us-gaap_AvailableforsaleSecuritiesMember_579A07C84C9459BDAF544FF1AB8CCFFA" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward" xlink:label="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward_F7FF8332C545583B8159F57326FA4A52" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems_1427C51D9A405AAA892316E399413ADB" xlink:to="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward_F7FF8332C545583B8159F57326FA4A52" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue" xlink:label="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue_E903AC509E765B7AA6A168FBCDF98F9E" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward_F7FF8332C545583B8159F57326FA4A52" xlink:to="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue_E903AC509E765B7AA6A168FBCDF98F9E" xlink:type="arc" />
    <link:loc xlink:href="ucbi-20190930.xsd#ucbi_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetBusinessCombinationAndProvisionalAdjustment" xlink:label="loc_ucbi_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetBusinessCombinationAndProvisionalAdjustment_E99E29FDFB405207A70FFD389E358D1E" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward_F7FF8332C545583B8159F57326FA4A52" xlink:to="loc_ucbi_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetBusinessCombinationAndProvisionalAdjustment_E99E29FDFB405207A70FFD389E358D1E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetIssues" xlink:label="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetIssues_96B7B258469D5E3692B319C4A6F6A6C3" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward_F7FF8332C545583B8159F57326FA4A52" xlink:to="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetIssues_96B7B258469D5E3692B319C4A6F6A6C3" xlink:type="arc" />
    <link:loc xlink:href="ucbi-20190930.xsd#ucbi_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSalesAndSettlements" xlink:label="loc_ucbi_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSalesAndSettlements_6D0067B58A6450BBBF590BD9C7C87BE6" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward_F7FF8332C545583B8159F57326FA4A52" xlink:to="loc_ucbi_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSalesAndSettlements_6D0067B58A6450BBBF590BD9C7C87BE6" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInOtherComprehensiveIncomeLoss" xlink:label="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInOtherComprehensiveIncomeLoss_A8AE3680AD1A5326BE8618BD12845E3F" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward_F7FF8332C545583B8159F57326FA4A52" xlink:to="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInOtherComprehensiveIncomeLoss_A8AE3680AD1A5326BE8618BD12845E3F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings1" xlink:label="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings1_7790716DF7F15E7889097D53E2A01C76" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward_F7FF8332C545583B8159F57326FA4A52" xlink:to="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings1_7790716DF7F15E7889097D53E2A01C76" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward" xlink:label="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward_CE33FB42A2F75435A9FE1024A2264F19" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems_1427C51D9A405AAA892316E399413ADB" xlink:to="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward_CE33FB42A2F75435A9FE1024A2264F19" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue" xlink:label="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue_158628BF76DC53679E5BA648E4DE5416" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward_CE33FB42A2F75435A9FE1024A2264F19" xlink:to="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue_158628BF76DC53679E5BA648E4DE5416" xlink:type="arc" />
    <link:loc xlink:href="ucbi-20190930.xsd#ucbi_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityBusinessCombinationAndProvisionalAdjustment" xlink:label="loc_ucbi_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityBusinessCombinationAndProvisionalAdjustment_E53B1998FED75A3F9845EBBE1C746834" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward_CE33FB42A2F75435A9FE1024A2264F19" xlink:to="loc_ucbi_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityBusinessCombinationAndProvisionalAdjustment_E53B1998FED75A3F9845EBBE1C746834" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityIssues" xlink:label="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityIssues_990CE2D73ECB5A0F82648435D0BBEBCD" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward_CE33FB42A2F75435A9FE1024A2264F19" xlink:to="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityIssues_990CE2D73ECB5A0F82648435D0BBEBCD" xlink:type="arc" />
    <link:loc xlink:href="ucbi-20190930.xsd#ucbi_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilitySalesAndSettlements" xlink:label="loc_ucbi_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilitySalesAndSettlements_ABEC192801295ECD9F0F1FC1E5ED2C06" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward_CE33FB42A2F75435A9FE1024A2264F19" xlink:to="loc_ucbi_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilitySalesAndSettlements_ABEC192801295ECD9F0F1FC1E5ED2C06" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityGainLossIncludedInOtherComprehensiveIncome" xlink:label="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityGainLossIncludedInOtherComprehensiveIncome_A72DDD4B622D5336BA510FB6D8AACB04" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward_CE33FB42A2F75435A9FE1024A2264F19" xlink:to="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityGainLossIncludedInOtherComprehensiveIncome_A72DDD4B622D5336BA510FB6D8AACB04" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityGainLossIncludedInEarnings" xlink:label="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityGainLossIncludedInEarnings_23CDEFB4246452E5AEC08D019A460F73" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward_CE33FB42A2F75435A9FE1024A2264F19" xlink:to="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityGainLossIncludedInEarnings_23CDEFB4246452E5AEC08D019A460F73" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://ucbi.com/role/AssetsAndLiabilitiesMeasuredAtFairValueTables" xlink:type="extended" />
  <link:definitionLink xlink:role="http://ucbi.com/role/BalanceSheetOffsettingAndRepurchaseAgreementsAccountedForAsSecuredBorrowings" xlink:type="extended" />
  <link:definitionLink xlink:role="http://ucbi.com/role/BalanceSheetOffsettingAndRepurchaseAgreementsAccountedForAsSecuredBorrowingsNarrativeDetails" xlink:type="extended" />
  <link:definitionLink xlink:role="http://ucbi.com/role/BalanceSheetOffsettingAndRepurchaseAgreementsAccountedForAsSecuredBorrowingsRepurchaseAgreementsAccountedForAsSecuredBorrowingsDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AssetsSoldUnderAgreementsToRepurchaseLineItems" xlink:label="loc_us-gaap_AssetsSoldUnderAgreementsToRepurchaseLineItems_A9682BED86EE515299DF304FB49E0470" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ScheduleOfAssetsSoldUnderAgreementsToRepurchaseTable" xlink:label="loc_us-gaap_ScheduleOfAssetsSoldUnderAgreementsToRepurchaseTable_E97C6BAAFEDB521395BCE12E2E5265AF" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_AssetsSoldUnderAgreementsToRepurchaseLineItems_A9682BED86EE515299DF304FB49E0470" xlink:to="loc_us-gaap_ScheduleOfAssetsSoldUnderAgreementsToRepurchaseTable_E97C6BAAFEDB521395BCE12E2E5265AF" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FinancialInstrumentAxis" xlink:label="loc_us-gaap_FinancialInstrumentAxis_FFB645E75F3F518692CBD40BC0317986" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfAssetsSoldUnderAgreementsToRepurchaseTable_E97C6BAAFEDB521395BCE12E2E5265AF" xlink:to="loc_us-gaap_FinancialInstrumentAxis_FFB645E75F3F518692CBD40BC0317986" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_CA0B801B39CD61D57ED0F747E0B0D398_3639CE68F660501A8F4042849B1BEF0D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_FFB645E75F3F518692CBD40BC0317986" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_CA0B801B39CD61D57ED0F747E0B0D398_3639CE68F660501A8F4042849B1BEF0D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_B6DE627274A159DABFEDCF6830932E16" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_FFB645E75F3F518692CBD40BC0317986" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_B6DE627274A159DABFEDCF6830932E16" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_MortgageBackedSecuritiesMember" xlink:label="loc_us-gaap_MortgageBackedSecuritiesMember_DD249D8538B6543B9BF7F882DDB052BF" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_B6DE627274A159DABFEDCF6830932E16" xlink:to="loc_us-gaap_MortgageBackedSecuritiesMember_DD249D8538B6543B9BF7F882DDB052BF" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AssetsSoldUnderAgreementsToRepurchaseMaturityPeriodsAxis" xlink:label="loc_us-gaap_AssetsSoldUnderAgreementsToRepurchaseMaturityPeriodsAxis_8B05E1F3327E5ADCA3722BCF91D24C0E" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfAssetsSoldUnderAgreementsToRepurchaseTable_E97C6BAAFEDB521395BCE12E2E5265AF" xlink:to="loc_us-gaap_AssetsSoldUnderAgreementsToRepurchaseMaturityPeriodsAxis_8B05E1F3327E5ADCA3722BCF91D24C0E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AssetsSoldUnderAgreementsToRepurchaseMaturityPeriodDomain" xlink:label="loc_us-gaap_AssetsSoldUnderAgreementsToRepurchaseMaturityPeriodDomain_E7AED1EFB87CDBCB2C6AF747E0B02627_3639CE68F660501A8F4042849B1BEF0D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AssetsSoldUnderAgreementsToRepurchaseMaturityPeriodsAxis_8B05E1F3327E5ADCA3722BCF91D24C0E" xlink:to="loc_us-gaap_AssetsSoldUnderAgreementsToRepurchaseMaturityPeriodDomain_E7AED1EFB87CDBCB2C6AF747E0B02627_3639CE68F660501A8F4042849B1BEF0D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AssetsSoldUnderAgreementsToRepurchaseMaturityPeriodDomain" xlink:label="loc_us-gaap_AssetsSoldUnderAgreementsToRepurchaseMaturityPeriodDomain_C6CACB7DA2C553E3911ED2642BDC2413" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AssetsSoldUnderAgreementsToRepurchaseMaturityPeriodsAxis_8B05E1F3327E5ADCA3722BCF91D24C0E" xlink:to="loc_us-gaap_AssetsSoldUnderAgreementsToRepurchaseMaturityPeriodDomain_C6CACB7DA2C553E3911ED2642BDC2413" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_MaturityOvernightMember" xlink:label="loc_us-gaap_MaturityOvernightMember_FD30DBA1F48150C2826F6F934F9D5FFA" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsSoldUnderAgreementsToRepurchaseMaturityPeriodDomain_C6CACB7DA2C553E3911ED2642BDC2413" xlink:to="loc_us-gaap_MaturityOvernightMember_FD30DBA1F48150C2826F6F934F9D5FFA" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_MaturityUpTo30DaysMember" xlink:label="loc_us-gaap_MaturityUpTo30DaysMember_50BA3C2890285EFBBFD9A73F136D7D60" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsSoldUnderAgreementsToRepurchaseMaturityPeriodDomain_C6CACB7DA2C553E3911ED2642BDC2413" xlink:to="loc_us-gaap_MaturityUpTo30DaysMember_50BA3C2890285EFBBFD9A73F136D7D60" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_Maturity30To90DaysMember" xlink:label="loc_us-gaap_Maturity30To90DaysMember_337F899E5C4B55DD836902972A4AD76A" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsSoldUnderAgreementsToRepurchaseMaturityPeriodDomain_C6CACB7DA2C553E3911ED2642BDC2413" xlink:to="loc_us-gaap_Maturity30To90DaysMember_337F899E5C4B55DD836902972A4AD76A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_MaturityOver90DaysMember" xlink:label="loc_us-gaap_MaturityOver90DaysMember_72E24CCC36755459B55171AB5EB15B39" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsSoldUnderAgreementsToRepurchaseMaturityPeriodDomain_C6CACB7DA2C553E3911ED2642BDC2413" xlink:to="loc_us-gaap_MaturityOver90DaysMember_72E24CCC36755459B55171AB5EB15B39" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SecuritiesSoldUnderAgreementsToRepurchaseGrossIncludingNotSubjectToMasterNettingArrangement" xlink:label="loc_us-gaap_SecuritiesSoldUnderAgreementsToRepurchaseGrossIncludingNotSubjectToMasterNettingArrangement_0CA50162F39B5E5A82EDDE1D881BF707" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsSoldUnderAgreementsToRepurchaseLineItems_A9682BED86EE515299DF304FB49E0470" xlink:to="loc_us-gaap_SecuritiesSoldUnderAgreementsToRepurchaseGrossIncludingNotSubjectToMasterNettingArrangement_0CA50162F39B5E5A82EDDE1D881BF707" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SecuritiesLoanedGrossIncludingNotSubjectToMasterNettingArrangement" xlink:label="loc_us-gaap_SecuritiesLoanedGrossIncludingNotSubjectToMasterNettingArrangement_C52C81A2E4D85B9A8CF54BBAFA56DA0A" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsSoldUnderAgreementsToRepurchaseLineItems_A9682BED86EE515299DF304FB49E0470" xlink:to="loc_us-gaap_SecuritiesLoanedGrossIncludingNotSubjectToMasterNettingArrangement_C52C81A2E4D85B9A8CF54BBAFA56DA0A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SecuritiesLoanedAndSecuritiesSoldUnderAgreementToRepurchaseGrossIncludingNotSubjectToMasterNettingArrangement" xlink:label="loc_us-gaap_SecuritiesLoanedAndSecuritiesSoldUnderAgreementToRepurchaseGrossIncludingNotSubjectToMasterNettingArrangement_9BF792237D0E59EFBC619A379B3B96F6" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsSoldUnderAgreementsToRepurchaseLineItems_A9682BED86EE515299DF304FB49E0470" xlink:to="loc_us-gaap_SecuritiesLoanedAndSecuritiesSoldUnderAgreementToRepurchaseGrossIncludingNotSubjectToMasterNettingArrangement_9BF792237D0E59EFBC619A379B3B96F6" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://ucbi.com/role/BalanceSheetOffsettingAndRepurchaseAgreementsAccountedForAsSecuredBorrowingsSummaryOfAmountsOutstandingUnderMasterNettingAgreementsDetails" xlink:type="extended" />
  <link:definitionLink xlink:role="http://ucbi.com/role/BalanceSheetOffsettingAndRepurchaseAgreementsAccountedForAsSecuredBorrowingsTables" xlink:type="extended" />
  <link:definitionLink xlink:role="http://ucbi.com/role/CommitmentsAndContingencies" xlink:type="extended" />
  <link:definitionLink xlink:role="http://ucbi.com/role/CommitmentsAndContingenciesContractualAmountOfOffBalanceSheetInstrumentsDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueOffBalanceSheetRisksDisclosureInformationLineItems" xlink:label="loc_us-gaap_FairValueOffBalanceSheetRisksDisclosureInformationLineItems_86974CBF2A3056D6BCD7CCC744ADDF1D" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ScheduleOfFairValueOffBalanceSheetRisksTable" xlink:label="loc_us-gaap_ScheduleOfFairValueOffBalanceSheetRisksTable_4463F5EB7A275745AA891BD9DF31A45B" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueOffBalanceSheetRisksDisclosureInformationLineItems_86974CBF2A3056D6BCD7CCC744ADDF1D" xlink:to="loc_us-gaap_ScheduleOfFairValueOffBalanceSheetRisksTable_4463F5EB7A275745AA891BD9DF31A45B" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FinancialInstrumentAxis" xlink:label="loc_us-gaap_FinancialInstrumentAxis_5D791ADC40A5515BAB1B29BAB71261FD" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFairValueOffBalanceSheetRisksTable_4463F5EB7A275745AA891BD9DF31A45B" xlink:to="loc_us-gaap_FinancialInstrumentAxis_5D791ADC40A5515BAB1B29BAB71261FD" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_783FD32AE7F3D101A51EF747E14E264D_3639CE68F660501A8F4042849B1BEF0D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_5D791ADC40A5515BAB1B29BAB71261FD" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_783FD32AE7F3D101A51EF747E14E264D_3639CE68F660501A8F4042849B1BEF0D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_70A5DDB91DAE5CA8AB0F005C8FE04F63" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_5D791ADC40A5515BAB1B29BAB71261FD" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_70A5DDB91DAE5CA8AB0F005C8FE04F63" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CommitmentsToExtendCreditMember" xlink:label="loc_us-gaap_CommitmentsToExtendCreditMember_79D989C69A295D7B92F3F1B630799BA7" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_70A5DDB91DAE5CA8AB0F005C8FE04F63" xlink:to="loc_us-gaap_CommitmentsToExtendCreditMember_79D989C69A295D7B92F3F1B630799BA7" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LetterOfCreditMember" xlink:label="loc_us-gaap_LetterOfCreditMember_CCBAC842F467598A9CA08E8AACCC11A8" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_70A5DDB91DAE5CA8AB0F005C8FE04F63" xlink:to="loc_us-gaap_LetterOfCreditMember_CCBAC842F467598A9CA08E8AACCC11A8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_UnusedCommitmentsToExtendCredit" xlink:label="loc_us-gaap_UnusedCommitmentsToExtendCredit_143B5F2DB79B534DB743FE62D5B77FF7" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueOffBalanceSheetRisksDisclosureInformationLineItems_86974CBF2A3056D6BCD7CCC744ADDF1D" xlink:to="loc_us-gaap_UnusedCommitmentsToExtendCredit_143B5F2DB79B534DB743FE62D5B77FF7" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://ucbi.com/role/CommitmentsAndContingenciesNarrativeDetails" xlink:type="extended" />
  <link:definitionLink xlink:role="http://ucbi.com/role/CommitmentsAndContingenciesTables" xlink:type="extended" />
  <link:definitionLink xlink:role="http://ucbi.com/role/CommonStock" xlink:type="extended" />
  <link:definitionLink xlink:role="http://ucbi.com/role/CommonStockDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_EquityClassOfTreasuryStockLineItems" xlink:label="loc_us-gaap_EquityClassOfTreasuryStockLineItems_20E6EDBFEE890025CDAF42BC2D67812E" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ClassOfTreasuryStockTable" xlink:label="loc_us-gaap_ClassOfTreasuryStockTable_11678CD14F886A54F2F542BC2D61F065" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_EquityClassOfTreasuryStockLineItems_20E6EDBFEE890025CDAF42BC2D67812E" xlink:to="loc_us-gaap_ClassOfTreasuryStockTable_11678CD14F886A54F2F542BC2D61F065" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SubsequentEventTypeAxis" xlink:label="loc_us-gaap_SubsequentEventTypeAxis_48145CE5499903A25E8942BCB23E278C" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ClassOfTreasuryStockTable_11678CD14F886A54F2F542BC2D61F065" xlink:to="loc_us-gaap_SubsequentEventTypeAxis_48145CE5499903A25E8942BCB23E278C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SubsequentEventTypeDomain" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_5F56AD7C31DA99561D6742BCB24013A4_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_48145CE5499903A25E8942BCB23E278C" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_5F56AD7C31DA99561D6742BCB24013A4_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SubsequentEventTypeDomain" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_5F56AD7C31DA99561D6742BCB24013A4" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_48145CE5499903A25E8942BCB23E278C" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_5F56AD7C31DA99561D6742BCB24013A4" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SubsequentEventMember" xlink:label="loc_us-gaap_SubsequentEventMember_BC85E307CED7DC22D4FE42BCEA5BE928" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventTypeDomain_5F56AD7C31DA99561D6742BCB24013A4" xlink:to="loc_us-gaap_SubsequentEventMember_BC85E307CED7DC22D4FE42BCEA5BE928" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StockRepurchaseProgramAuthorizedAmount1" xlink:label="loc_us-gaap_StockRepurchaseProgramAuthorizedAmount1_FEF4CC69B3BABF8227D642AB11435BB4" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityClassOfTreasuryStockLineItems_20E6EDBFEE890025CDAF42BC2D67812E" xlink:to="loc_us-gaap_StockRepurchaseProgramAuthorizedAmount1_FEF4CC69B3BABF8227D642AB11435BB4" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_TreasuryStockSharesAcquired" xlink:label="loc_us-gaap_TreasuryStockSharesAcquired_4A6B6E3F1E6466007D6C42AB1143CCF9" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityClassOfTreasuryStockLineItems_20E6EDBFEE890025CDAF42BC2D67812E" xlink:to="loc_us-gaap_TreasuryStockSharesAcquired_4A6B6E3F1E6466007D6C42AB1143CCF9" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StockRepurchaseProgramRemainingAuthorizedRepurchaseAmount1" xlink:label="loc_us-gaap_StockRepurchaseProgramRemainingAuthorizedRepurchaseAmount1_70693CD4FAC2E8F3E18342AB11440C8E" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityClassOfTreasuryStockLineItems_20E6EDBFEE890025CDAF42BC2D67812E" xlink:to="loc_us-gaap_StockRepurchaseProgramRemainingAuthorizedRepurchaseAmount1_70693CD4FAC2E8F3E18342AB11440C8E" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://ucbi.com/role/ConsolidatedBalanceSheetsUnaudited" xlink:type="extended" />
  <link:definitionLink xlink:role="http://ucbi.com/role/ConsolidatedBalanceSheetsUnauditedParentheticals" xlink:type="extended" />
  <link:definitionLink xlink:role="http://ucbi.com/role/ConsolidatedStatementOfChangesInShareholdersEquityUnaudited" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StatementLineItems" xlink:label="loc_us-gaap_StatementLineItems_A27000B7DE16E880B5C93C0AA604C675" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StatementTable" xlink:label="loc_us-gaap_StatementTable_FBC6317E808F5112C33D3C0AA6021785" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_A27000B7DE16E880B5C93C0AA604C675" xlink:to="loc_us-gaap_StatementTable_FBC6317E808F5112C33D3C0AA6021785" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StatementEquityComponentsAxis" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_A5DDE47DAEB8DCB3FD5F3C0AA603E825" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_FBC6317E808F5112C33D3C0AA6021785" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_A5DDE47DAEB8DCB3FD5F3C0AA603E825" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_EquityComponentDomain" xlink:label="loc_us-gaap_EquityComponentDomain_EF4C2E246F847A74154B3C0AA603A23C_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_A5DDE47DAEB8DCB3FD5F3C0AA603E825" xlink:to="loc_us-gaap_EquityComponentDomain_EF4C2E246F847A74154B3C0AA603A23C_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_EquityComponentDomain" xlink:label="loc_us-gaap_EquityComponentDomain_EF4C2E246F847A74154B3C0AA603A23C" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_A5DDE47DAEB8DCB3FD5F3C0AA603E825" xlink:to="loc_us-gaap_EquityComponentDomain_EF4C2E246F847A74154B3C0AA603A23C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CommonStockMember" xlink:label="loc_us-gaap_CommonStockMember_59EFD7D983B2E06164583C0AA603DD94" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_EF4C2E246F847A74154B3C0AA603A23C" xlink:to="loc_us-gaap_CommonStockMember_59EFD7D983B2E06164583C0AA603DD94" xlink:type="arc" />
    <link:loc xlink:href="ucbi-20190930.xsd#ucbi_CommonStockIssuableMember" xlink:label="loc_ucbi_CommonStockIssuableMember_0BA6368AF0E24CE5D3FB3C0AA603ABCD" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_EF4C2E246F847A74154B3C0AA603A23C" xlink:to="loc_ucbi_CommonStockIssuableMember_0BA6368AF0E24CE5D3FB3C0AA603ABCD" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AdditionalPaidInCapitalMember" xlink:label="loc_us-gaap_AdditionalPaidInCapitalMember_914FA1D8DD3F51E8E1F53C0AA604EDB4" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_EF4C2E246F847A74154B3C0AA603A23C" xlink:to="loc_us-gaap_AdditionalPaidInCapitalMember_914FA1D8DD3F51E8E1F53C0AA604EDB4" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RetainedEarningsMember" xlink:label="loc_us-gaap_RetainedEarningsMember_3AE18FFBF945CFBAD8BD3C0AA6046DD3" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_EF4C2E246F847A74154B3C0AA603A23C" xlink:to="loc_us-gaap_RetainedEarningsMember_3AE18FFBF945CFBAD8BD3C0AA6046DD3" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeMember" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_A7F192ACCBE4408ADFB13C0AA604D9DB" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_EF4C2E246F847A74154B3C0AA603A23C" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_A7F192ACCBE4408ADFB13C0AA604D9DB" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_IncreaseDecreaseInStockholdersEquityRollForward" xlink:label="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_52B9DEC9F5FFD33FA7253C0AA6041EF4" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_A27000B7DE16E880B5C93C0AA604C675" xlink:to="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_52B9DEC9F5FFD33FA7253C0AA6041EF4" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StockholdersEquity" xlink:label="loc_us-gaap_StockholdersEquity_57458D38DED0EBBE075F3C0AA605C93E" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_52B9DEC9F5FFD33FA7253C0AA6041EF4" xlink:to="loc_us-gaap_StockholdersEquity_57458D38DED0EBBE075F3C0AA605C93E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_NetIncomeLoss" xlink:label="loc_us-gaap_NetIncomeLoss_1553E4196BE6C34865ED3C0AA605745B" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_52B9DEC9F5FFD33FA7253C0AA6041EF4" xlink:to="loc_us-gaap_NetIncomeLoss_1553E4196BE6C34865ED3C0AA605745B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent_775A5EF4B9DE460693B93C0AA60577B0" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_52B9DEC9F5FFD33FA7253C0AA6041EF4" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent_775A5EF4B9DE460693B93C0AA60577B0" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised_39265FBDAA92A342DCC93C0AA6058489" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_52B9DEC9F5FFD33FA7253C0AA6041EF4" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised_39265FBDAA92A342DCC93C0AA6058489" xlink:type="arc" />
    <link:loc xlink:href="ucbi-20190930.xsd#ucbi_CommonStockIssuedToDividendReinvestmentPlanAndEmployeeBenefitPlansValue" xlink:label="loc_ucbi_CommonStockIssuedToDividendReinvestmentPlanAndEmployeeBenefitPlansValue_3D32CC60A1D916E99C2B3C0AA6058339" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_52B9DEC9F5FFD33FA7253C0AA6041EF4" xlink:to="loc_ucbi_CommonStockIssuedToDividendReinvestmentPlanAndEmployeeBenefitPlansValue_3D32CC60A1D916E99C2B3C0AA6058339" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StockIssuedDuringPeriodValueAcquisitions" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueAcquisitions_DC2734FDA5EC2D038ED43C0AA6051466" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_52B9DEC9F5FFD33FA7253C0AA6041EF4" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueAcquisitions_DC2734FDA5EC2D038ED43C0AA6051466" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue" xlink:label="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_7B6C51DDA811AF5F30463C0AA605ACC7" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_52B9DEC9F5FFD33FA7253C0AA6041EF4" xlink:to="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_7B6C51DDA811AF5F30463C0AA605ACC7" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StockIssuedDuringPeriodValueRestrictedStockAwardNetOfForfeitures" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueRestrictedStockAwardNetOfForfeitures_D8EA0D7082D3F98EE21A3C0AA606B50F" xlink:type="locator" />
    <link:definitionArc order="8" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_52B9DEC9F5FFD33FA7253C0AA6041EF4" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueRestrictedStockAwardNetOfForfeitures_D8EA0D7082D3F98EE21A3C0AA606B50F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StockRepurchasedAndRetiredDuringPeriodValue" xlink:label="loc_us-gaap_StockRepurchasedAndRetiredDuringPeriodValue_B71254F521635389245F3C0AA606B143" xlink:type="locator" />
    <link:definitionArc order="9" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_52B9DEC9F5FFD33FA7253C0AA6041EF4" xlink:to="loc_us-gaap_StockRepurchasedAndRetiredDuringPeriodValue_B71254F521635389245F3C0AA606B143" xlink:type="arc" />
    <link:loc xlink:href="ucbi-20190930.xsd#ucbi_DeferredCompensationPlanNetIncludingDividendEquivalents" xlink:label="loc_ucbi_DeferredCompensationPlanNetIncludingDividendEquivalents_57BDDB100B5DD756A8363C0AA606D412" xlink:type="locator" />
    <link:definitionArc order="10" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_52B9DEC9F5FFD33FA7253C0AA6041EF4" xlink:to="loc_ucbi_DeferredCompensationPlanNetIncludingDividendEquivalents_57BDDB100B5DD756A8363C0AA606D412" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StockIssuedDuringPeriodValueShareBasedCompensation" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueShareBasedCompensation_09F648E26FE648E1953A3C0AA60674C6" xlink:type="locator" />
    <link:definitionArc order="11" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_52B9DEC9F5FFD33FA7253C0AA6041EF4" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueShareBasedCompensation_09F648E26FE648E1953A3C0AA60674C6" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DividendsCommonStockCash" xlink:label="loc_us-gaap_DividendsCommonStockCash_D5F7638DD0D116E963FB3C0AA6063680" xlink:type="locator" />
    <link:definitionArc order="12" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_52B9DEC9F5FFD33FA7253C0AA6041EF4" xlink:to="loc_us-gaap_DividendsCommonStockCash_D5F7638DD0D116E963FB3C0AA6063680" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption" xlink:label="loc_us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption_01C5C57636ABBB93AFCB3C0AA6060184" xlink:type="locator" />
    <link:definitionArc order="13" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_52B9DEC9F5FFD33FA7253C0AA6041EF4" xlink:to="loc_us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption_01C5C57636ABBB93AFCB3C0AA6060184" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://ucbi.com/role/ConsolidatedStatementOfChangesInShareholdersEquityUnauditedParentheticals" xlink:type="extended" />
  <link:definitionLink xlink:role="http://ucbi.com/role/ConsolidatedStatementsOfCashFlowsUnaudited" xlink:type="extended" />
  <link:definitionLink xlink:role="http://ucbi.com/role/ConsolidatedStatementsOfComprehensiveIncomeUnaudited" xlink:type="extended" />
  <link:definitionLink xlink:role="http://ucbi.com/role/ConsolidatedStatementsOfIncomeUnaudited" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StatementLineItems" xlink:label="loc_us-gaap_StatementLineItems_D800ADE6D906BAE602E542AB136AF991" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StatementTable" xlink:label="loc_us-gaap_StatementTable_114678542424B1D47C7142AB1363D6E8" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_D800ADE6D906BAE602E542AB136AF991" xlink:to="loc_us-gaap_StatementTable_114678542424B1D47C7142AB1363D6E8" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LoansInsuredOrGuaranteedByGovernmentAuthoritiesAxis" xlink:label="loc_us-gaap_LoansInsuredOrGuaranteedByGovernmentAuthoritiesAxis_E1EC4EDA2620F5419A7D42AB1364467C" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_114678542424B1D47C7142AB1363D6E8" xlink:to="loc_us-gaap_LoansInsuredOrGuaranteedByGovernmentAuthoritiesAxis_E1EC4EDA2620F5419A7D42AB1364467C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LoansInsuredOrGuaranteedByGovernmentAuthoritiesDomain" xlink:label="loc_us-gaap_LoansInsuredOrGuaranteedByGovernmentAuthoritiesDomain_75D896046D68409ABE9F42AB13647A46_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LoansInsuredOrGuaranteedByGovernmentAuthoritiesAxis_E1EC4EDA2620F5419A7D42AB1364467C" xlink:to="loc_us-gaap_LoansInsuredOrGuaranteedByGovernmentAuthoritiesDomain_75D896046D68409ABE9F42AB13647A46_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LoansInsuredOrGuaranteedByGovernmentAuthoritiesDomain" xlink:label="loc_us-gaap_LoansInsuredOrGuaranteedByGovernmentAuthoritiesDomain_75D896046D68409ABE9F42AB13647A46" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LoansInsuredOrGuaranteedByGovernmentAuthoritiesAxis_E1EC4EDA2620F5419A7D42AB1364467C" xlink:to="loc_us-gaap_LoansInsuredOrGuaranteedByGovernmentAuthoritiesDomain_75D896046D68409ABE9F42AB13647A46" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_UsGovernmentAgencyInsuredLoansMember" xlink:label="loc_us-gaap_UsGovernmentAgencyInsuredLoansMember_A1F5D8F5DB3BDA992F8042AB1365D0EA" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LoansInsuredOrGuaranteedByGovernmentAuthoritiesDomain_75D896046D68409ABE9F42AB13647A46" xlink:to="loc_us-gaap_UsGovernmentAgencyInsuredLoansMember_A1F5D8F5DB3BDA992F8042AB1365D0EA" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_ProductOrServiceAxis" xlink:label="loc_srt_ProductOrServiceAxis_0E5FDD9296458F75CF7942AB1363BE5C" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_114678542424B1D47C7142AB1363D6E8" xlink:to="loc_srt_ProductOrServiceAxis_0E5FDD9296458F75CF7942AB1363BE5C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_ProductsAndServicesDomain" xlink:label="loc_srt_ProductsAndServicesDomain_9F7FD6E20F231636C1EF42AB1363924C_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_0E5FDD9296458F75CF7942AB1363BE5C" xlink:to="loc_srt_ProductsAndServicesDomain_9F7FD6E20F231636C1EF42AB1363924C_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_ProductsAndServicesDomain" xlink:label="loc_srt_ProductsAndServicesDomain_9F7FD6E20F231636C1EF42AB1363924C" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_0E5FDD9296458F75CF7942AB1363BE5C" xlink:to="loc_srt_ProductsAndServicesDomain_9F7FD6E20F231636C1EF42AB1363924C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DepositAccountMember" xlink:label="loc_us-gaap_DepositAccountMember_CDD6125B8CB516E9A01B42AB1364B06E" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_9F7FD6E20F231636C1EF42AB1363924C" xlink:to="loc_us-gaap_DepositAccountMember_CDD6125B8CB516E9A01B42AB1364B06E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_MortgageBankingMember" xlink:label="loc_us-gaap_MortgageBankingMember_D17ABA9CE4B86ACCC3C942AB136403DE" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_9F7FD6E20F231636C1EF42AB1363924C" xlink:to="loc_us-gaap_MortgageBankingMember_D17ABA9CE4B86ACCC3C942AB136403DE" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_InterestAndDividendIncomeOperatingAbstract" xlink:label="loc_us-gaap_InterestAndDividendIncomeOperatingAbstract_20A3884AEB09F837AE7E42AB136AEF1E" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_D800ADE6D906BAE602E542AB136AF991" xlink:to="loc_us-gaap_InterestAndDividendIncomeOperatingAbstract_20A3884AEB09F837AE7E42AB136AEF1E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_InterestAndFeeIncomeLoansAndLeases" xlink:label="loc_us-gaap_InterestAndFeeIncomeLoansAndLeases_AABE7BD891ED9981595142AB136B6E27" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InterestAndDividendIncomeOperatingAbstract_20A3884AEB09F837AE7E42AB136AEF1E" xlink:to="loc_us-gaap_InterestAndFeeIncomeLoansAndLeases_AABE7BD891ED9981595142AB136B6E27" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_InterestAndDividendIncomeSecurities" xlink:label="loc_us-gaap_InterestAndDividendIncomeSecurities_46E52A4D4E8C7105EF7742AB136BB935" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InterestAndDividendIncomeOperatingAbstract_20A3884AEB09F837AE7E42AB136AEF1E" xlink:to="loc_us-gaap_InterestAndDividendIncomeSecurities_46E52A4D4E8C7105EF7742AB136BB935" xlink:type="arc" />
    <link:loc xlink:href="ucbi-20190930.xsd#ucbi_FederalFundsSoldCommercialPaperAndDepositsInBanks" xlink:label="loc_ucbi_FederalFundsSoldCommercialPaperAndDepositsInBanks_01F185ED221BEF957EC342AB136B19A8" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InterestAndDividendIncomeOperatingAbstract_20A3884AEB09F837AE7E42AB136AEF1E" xlink:to="loc_ucbi_FederalFundsSoldCommercialPaperAndDepositsInBanks_01F185ED221BEF957EC342AB136B19A8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_InterestAndDividendIncomeOperating" xlink:label="loc_us-gaap_InterestAndDividendIncomeOperating_D1F5677D266E3DF0111842AB136BF5D7" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InterestAndDividendIncomeOperatingAbstract_20A3884AEB09F837AE7E42AB136AEF1E" xlink:to="loc_us-gaap_InterestAndDividendIncomeOperating_D1F5677D266E3DF0111842AB136BF5D7" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_InterestExpenseAbstract" xlink:label="loc_us-gaap_InterestExpenseAbstract_157C909717D1B003EAD942AB136B0A9B" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_D800ADE6D906BAE602E542AB136AF991" xlink:to="loc_us-gaap_InterestExpenseAbstract_157C909717D1B003EAD942AB136B0A9B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_InterestExpenseDeposits" xlink:label="loc_us-gaap_InterestExpenseDeposits_F3884E06A4B80672333C42AB136B9A8B" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InterestExpenseAbstract_157C909717D1B003EAD942AB136B0A9B" xlink:to="loc_us-gaap_InterestExpenseDeposits_F3884E06A4B80672333C42AB136B9A8B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_InterestExpenseShortTermBorrowings" xlink:label="loc_us-gaap_InterestExpenseShortTermBorrowings_AF391919D00DC1447B1242AB136CDEDD" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InterestExpenseAbstract_157C909717D1B003EAD942AB136B0A9B" xlink:to="loc_us-gaap_InterestExpenseShortTermBorrowings_AF391919D00DC1447B1242AB136CDEDD" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_InterestExpenseFederalHomeLoanBankAndFederalReserveBankAdvancesShortTerm" xlink:label="loc_us-gaap_InterestExpenseFederalHomeLoanBankAndFederalReserveBankAdvancesShortTerm_431E72764142D449F61D42AB136CDB9F" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InterestExpenseAbstract_157C909717D1B003EAD942AB136B0A9B" xlink:to="loc_us-gaap_InterestExpenseFederalHomeLoanBankAndFederalReserveBankAdvancesShortTerm_431E72764142D449F61D42AB136CDB9F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_InterestExpenseLongTermDebt" xlink:label="loc_us-gaap_InterestExpenseLongTermDebt_77B9AAB2610A1444A33A42AB136C3340" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InterestExpenseAbstract_157C909717D1B003EAD942AB136B0A9B" xlink:to="loc_us-gaap_InterestExpenseLongTermDebt_77B9AAB2610A1444A33A42AB136C3340" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_InterestExpense" xlink:label="loc_us-gaap_InterestExpense_DFD593FF4A4BDF74D4E442AB136C39FF" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InterestExpenseAbstract_157C909717D1B003EAD942AB136B0A9B" xlink:to="loc_us-gaap_InterestExpense_DFD593FF4A4BDF74D4E442AB136C39FF" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_InterestIncomeExpenseNet" xlink:label="loc_us-gaap_InterestIncomeExpenseNet_CFCBB51913380AB058FF42AB136CF63A" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_D800ADE6D906BAE602E542AB136AF991" xlink:to="loc_us-gaap_InterestIncomeExpenseNet_CFCBB51913380AB058FF42AB136CF63A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ProvisionForLoanAndLeaseLosses" xlink:label="loc_us-gaap_ProvisionForLoanAndLeaseLosses_4D360DEE2917F2FE648F42AB136D3F57" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_D800ADE6D906BAE602E542AB136AF991" xlink:to="loc_us-gaap_ProvisionForLoanAndLeaseLosses_4D360DEE2917F2FE648F42AB136D3F57" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_InterestIncomeExpenseAfterProvisionForLoanLoss" xlink:label="loc_us-gaap_InterestIncomeExpenseAfterProvisionForLoanLoss_A5F19CFE1CF57660E45342AB136D97AA" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_D800ADE6D906BAE602E542AB136AF991" xlink:to="loc_us-gaap_InterestIncomeExpenseAfterProvisionForLoanLoss_A5F19CFE1CF57660E45342AB136D97AA" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_NoninterestIncomeAbstract" xlink:label="loc_us-gaap_NoninterestIncomeAbstract_9CBD065D5EF3F91E0D2B42AB136D50FD" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_D800ADE6D906BAE602E542AB136AF991" xlink:to="loc_us-gaap_NoninterestIncomeAbstract_9CBD065D5EF3F91E0D2B42AB136D50FD" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_NoninterestIncomeOther" xlink:label="loc_us-gaap_NoninterestIncomeOther_EF948CB5AB0BEE1688C642AB136DF393" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NoninterestIncomeAbstract_9CBD065D5EF3F91E0D2B42AB136D50FD" xlink:to="loc_us-gaap_NoninterestIncomeOther_EF948CB5AB0BEE1688C642AB136DF393" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BrokerageCommissionsRevenue" xlink:label="loc_us-gaap_BrokerageCommissionsRevenue_80055B9B2B7F09D3CC1342AB136D6DFF" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NoninterestIncomeAbstract_9CBD065D5EF3F91E0D2B42AB136D50FD" xlink:to="loc_us-gaap_BrokerageCommissionsRevenue_80055B9B2B7F09D3CC1342AB136D6DFF" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_GainLossOnSalesOfLoansNet" xlink:label="loc_us-gaap_GainLossOnSalesOfLoansNet_1C159BDF084AAD4B3B4A43026EE2FD65" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NoninterestIncomeAbstract_9CBD065D5EF3F91E0D2B42AB136D50FD" xlink:to="loc_us-gaap_GainLossOnSalesOfLoansNet_1C159BDF084AAD4B3B4A43026EE2FD65" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtSecuritiesAvailableForSaleRealizedGainLoss" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleRealizedGainLoss_BA71A4F2AA6C1B91F41842AB136EB42E" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NoninterestIncomeAbstract_9CBD065D5EF3F91E0D2B42AB136D50FD" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleRealizedGainLoss_BA71A4F2AA6C1B91F41842AB136EB42E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_NoninterestIncomeOtherOperatingIncome" xlink:label="loc_us-gaap_NoninterestIncomeOtherOperatingIncome_2D740672494CC3F758FE42AB136E0BC3" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NoninterestIncomeAbstract_9CBD065D5EF3F91E0D2B42AB136D50FD" xlink:to="loc_us-gaap_NoninterestIncomeOtherOperatingIncome_2D740672494CC3F758FE42AB136E0BC3" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_NoninterestIncome" xlink:label="loc_us-gaap_NoninterestIncome_92422A626FE4BF84E28342AB136E3777" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NoninterestIncomeAbstract_9CBD065D5EF3F91E0D2B42AB136D50FD" xlink:to="loc_us-gaap_NoninterestIncome_92422A626FE4BF84E28342AB136E3777" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_Revenues" xlink:label="loc_us-gaap_Revenues_5FF987AE06861CC1B4C242AB136E817D" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_D800ADE6D906BAE602E542AB136AF991" xlink:to="loc_us-gaap_Revenues_5FF987AE06861CC1B4C242AB136E817D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OperatingExpensesAbstract" xlink:label="loc_us-gaap_OperatingExpensesAbstract_83CFF5D951A90A0FCF8242AB136ECF13" xlink:type="locator" />
    <link:definitionArc order="8" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_D800ADE6D906BAE602E542AB136AF991" xlink:to="loc_us-gaap_OperatingExpensesAbstract_83CFF5D951A90A0FCF8242AB136ECF13" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LaborAndRelatedExpense" xlink:label="loc_us-gaap_LaborAndRelatedExpense_04B19D52C0E9DDB11E3E42AB136F12FD" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingExpensesAbstract_83CFF5D951A90A0FCF8242AB136ECF13" xlink:to="loc_us-gaap_LaborAndRelatedExpense_04B19D52C0E9DDB11E3E42AB136F12FD" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CommunicationsAndInformationTechnology" xlink:label="loc_us-gaap_CommunicationsAndInformationTechnology_8B51EC458E753E786EE142AB136F3890" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingExpensesAbstract_83CFF5D951A90A0FCF8242AB136ECF13" xlink:to="loc_us-gaap_CommunicationsAndInformationTechnology_8B51EC458E753E786EE142AB136F3890" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OccupancyNet" xlink:label="loc_us-gaap_OccupancyNet_999FA93EDD57635F1AD642AB136F4515" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingExpensesAbstract_83CFF5D951A90A0FCF8242AB136ECF13" xlink:to="loc_us-gaap_OccupancyNet_999FA93EDD57635F1AD642AB136F4515" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_MarketingAndAdvertisingExpense" xlink:label="loc_us-gaap_MarketingAndAdvertisingExpense_C72A0F4EB492C704ECCF42AB136F020D" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingExpensesAbstract_83CFF5D951A90A0FCF8242AB136ECF13" xlink:to="loc_us-gaap_MarketingAndAdvertisingExpense_C72A0F4EB492C704ECCF42AB136F020D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SuppliesAndPostageExpense" xlink:label="loc_us-gaap_SuppliesAndPostageExpense_C0D2AFA58A264098613F42AB136F2932" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingExpensesAbstract_83CFF5D951A90A0FCF8242AB136ECF13" xlink:to="loc_us-gaap_SuppliesAndPostageExpense_C0D2AFA58A264098613F42AB136F2932" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ProfessionalFees" xlink:label="loc_us-gaap_ProfessionalFees_B1B88C377F83F780260B42AB136F80DF" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingExpensesAbstract_83CFF5D951A90A0FCF8242AB136ECF13" xlink:to="loc_us-gaap_ProfessionalFees_B1B88C377F83F780260B42AB136F80DF" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FederalDepositInsuranceCorporationPremiumExpense" xlink:label="loc_us-gaap_FederalDepositInsuranceCorporationPremiumExpense_4F3A1C70D457A2888B6A42AB1370A981" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingExpensesAbstract_83CFF5D951A90A0FCF8242AB136ECF13" xlink:to="loc_us-gaap_FederalDepositInsuranceCorporationPremiumExpense_4F3A1C70D457A2888B6A42AB1370A981" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AmortizationOfIntangibleAssets" xlink:label="loc_us-gaap_AmortizationOfIntangibleAssets_69BF31ED3906B8D3547C42AB1370B0CE" xlink:type="locator" />
    <link:definitionArc order="8" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingExpensesAbstract_83CFF5D951A90A0FCF8242AB136ECF13" xlink:to="loc_us-gaap_AmortizationOfIntangibleAssets_69BF31ED3906B8D3547C42AB1370B0CE" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessCombinationAcquisitionRelatedCosts" xlink:label="loc_us-gaap_BusinessCombinationAcquisitionRelatedCosts_E6BCD0B5A07E2799DE3C42AB1370E3BA" xlink:type="locator" />
    <link:definitionArc order="9" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingExpensesAbstract_83CFF5D951A90A0FCF8242AB136ECF13" xlink:to="loc_us-gaap_BusinessCombinationAcquisitionRelatedCosts_E6BCD0B5A07E2799DE3C42AB1370E3BA" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OtherNoninterestExpense" xlink:label="loc_us-gaap_OtherNoninterestExpense_68C68952484D31B1D2AF42AB1370FE24" xlink:type="locator" />
    <link:definitionArc order="10" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingExpensesAbstract_83CFF5D951A90A0FCF8242AB136ECF13" xlink:to="loc_us-gaap_OtherNoninterestExpense_68C68952484D31B1D2AF42AB1370FE24" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_NoninterestExpense" xlink:label="loc_us-gaap_NoninterestExpense_65F92DEA67D099A23D3142AB1370AA2B" xlink:type="locator" />
    <link:definitionArc order="11" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingExpensesAbstract_83CFF5D951A90A0FCF8242AB136ECF13" xlink:to="loc_us-gaap_NoninterestExpense_65F92DEA67D099A23D3142AB1370AA2B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments" xlink:label="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments_D8F8D52343EFD1260B2042AB1371CC21" xlink:type="locator" />
    <link:definitionArc order="9" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_D800ADE6D906BAE602E542AB136AF991" xlink:to="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments_D8F8D52343EFD1260B2042AB1371CC21" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_IncomeTaxExpenseBenefit" xlink:label="loc_us-gaap_IncomeTaxExpenseBenefit_C1D172472BE8F868281742AB1371FE19" xlink:type="locator" />
    <link:definitionArc order="10" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_D800ADE6D906BAE602E542AB136AF991" xlink:to="loc_us-gaap_IncomeTaxExpenseBenefit_C1D172472BE8F868281742AB1371FE19" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_NetIncomeLoss" xlink:label="loc_us-gaap_NetIncomeLoss_8654E234CE7F791103C342AB1371A4AA" xlink:type="locator" />
    <link:definitionArc order="11" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_D800ADE6D906BAE602E542AB136AF991" xlink:to="loc_us-gaap_NetIncomeLoss_8654E234CE7F791103C342AB1371A4AA" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic" xlink:label="loc_us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic_1FA56897E0CB5814299542AB1371DB4B" xlink:type="locator" />
    <link:definitionArc order="12" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_D800ADE6D906BAE602E542AB136AF991" xlink:to="loc_us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic_1FA56897E0CB5814299542AB1371DB4B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_EarningsPerShareAbstract" xlink:label="loc_us-gaap_EarningsPerShareAbstract_824DBBE524DA6789766A42AB1371FA07" xlink:type="locator" />
    <link:definitionArc order="13" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_D800ADE6D906BAE602E542AB136AF991" xlink:to="loc_us-gaap_EarningsPerShareAbstract_824DBBE524DA6789766A42AB1371FA07" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_EarningsPerShareBasic" xlink:label="loc_us-gaap_EarningsPerShareBasic_800F0CB45A4E074DC06142AB1371A106" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareAbstract_824DBBE524DA6789766A42AB1371FA07" xlink:to="loc_us-gaap_EarningsPerShareBasic_800F0CB45A4E074DC06142AB1371A106" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_EarningsPerShareDiluted" xlink:label="loc_us-gaap_EarningsPerShareDiluted_A085CF1D69A72E68E52C42AB1372976E" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareAbstract_824DBBE524DA6789766A42AB1371FA07" xlink:to="loc_us-gaap_EarningsPerShareDiluted_A085CF1D69A72E68E52C42AB1372976E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_WeightedAverageNumberOfSharesOutstandingAbstract" xlink:label="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingAbstract_7D006B8354D0B22F7E4C42AB1372D760" xlink:type="locator" />
    <link:definitionArc order="14" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_D800ADE6D906BAE602E542AB136AF991" xlink:to="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingAbstract_7D006B8354D0B22F7E4C42AB1372D760" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_WeightedAverageNumberOfSharesOutstandingBasic" xlink:label="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_AF79D0C84513039DF1B742AB13721922" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingAbstract_7D006B8354D0B22F7E4C42AB1372D760" xlink:to="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_AF79D0C84513039DF1B742AB13721922" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding" xlink:label="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_7CD0EA4F4FB9185E342E42AB13724DF0" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingAbstract_7D006B8354D0B22F7E4C42AB1372D760" xlink:to="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_7CD0EA4F4FB9185E342E42AB13724DF0" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://ucbi.com/role/ConsolidatedStatementsOfIncomeUnauditedParentheticals" xlink:type="extended" />
  <link:definitionLink xlink:role="http://ucbi.com/role/CoverPage" xlink:type="extended" />
  <link:definitionLink xlink:role="http://ucbi.com/role/DerivativesAndHedgingActivities" xlink:type="extended" />
  <link:definitionLink xlink:role="http://ucbi.com/role/DerivativesAndHedgingActivitiesDerivativesDesignatedAsHedgingInstrumentsDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DerivativesFairValueLineItems" xlink:label="loc_us-gaap_DerivativesFairValueLineItems_6FFAEC31935356F4A36669DCD3360023" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValuesDerivativesBalanceSheetLocationByDerivativeContractTypeByHedgingDesignationTable" xlink:label="loc_us-gaap_FairValuesDerivativesBalanceSheetLocationByDerivativeContractTypeByHedgingDesignationTable_203E902252675B57AA72CCB5135FE82B" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DerivativesFairValueLineItems_6FFAEC31935356F4A36669DCD3360023" xlink:to="loc_us-gaap_FairValuesDerivativesBalanceSheetLocationByDerivativeContractTypeByHedgingDesignationTable_203E902252675B57AA72CCB5135FE82B" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_HedgingDesignationAxis" xlink:label="loc_us-gaap_HedgingDesignationAxis_22A99A4F5BEF51519739E1F6644BDDF7" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValuesDerivativesBalanceSheetLocationByDerivativeContractTypeByHedgingDesignationTable_203E902252675B57AA72CCB5135FE82B" xlink:to="loc_us-gaap_HedgingDesignationAxis_22A99A4F5BEF51519739E1F6644BDDF7" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_HedgingDesignationDomain" xlink:label="loc_us-gaap_HedgingDesignationDomain_826AB5299E99609BE6BA6D3297172D56_3639CE68F660501A8F4042849B1BEF0D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_HedgingDesignationAxis_22A99A4F5BEF51519739E1F6644BDDF7" xlink:to="loc_us-gaap_HedgingDesignationDomain_826AB5299E99609BE6BA6D3297172D56_3639CE68F660501A8F4042849B1BEF0D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_HedgingDesignationDomain" xlink:label="loc_us-gaap_HedgingDesignationDomain_B49A7A378D90528D9AC3DEFF5C4DF54D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_HedgingDesignationAxis_22A99A4F5BEF51519739E1F6644BDDF7" xlink:to="loc_us-gaap_HedgingDesignationDomain_B49A7A378D90528D9AC3DEFF5C4DF54D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DesignatedAsHedgingInstrumentMember" xlink:label="loc_us-gaap_DesignatedAsHedgingInstrumentMember_878E10A09FE155D9A2E112EAAF7B61EF" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HedgingDesignationDomain_B49A7A378D90528D9AC3DEFF5C4DF54D" xlink:to="loc_us-gaap_DesignatedAsHedgingInstrumentMember_878E10A09FE155D9A2E112EAAF7B61EF" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis" xlink:label="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_4A947661D0885EB388990A3372D4CF4D" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValuesDerivativesBalanceSheetLocationByDerivativeContractTypeByHedgingDesignationTable_203E902252675B57AA72CCB5135FE82B" xlink:to="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_4A947661D0885EB388990A3372D4CF4D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_HedgingRelationshipDomain" xlink:label="loc_us-gaap_HedgingRelationshipDomain_F9BE2B42CEFBA508345C6D329717F729_3639CE68F660501A8F4042849B1BEF0D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_4A947661D0885EB388990A3372D4CF4D" xlink:to="loc_us-gaap_HedgingRelationshipDomain_F9BE2B42CEFBA508345C6D329717F729_3639CE68F660501A8F4042849B1BEF0D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_HedgingRelationshipDomain" xlink:label="loc_us-gaap_HedgingRelationshipDomain_A5F3DD48B0FF55939033EE6E87AD3D53" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_4A947661D0885EB388990A3372D4CF4D" xlink:to="loc_us-gaap_HedgingRelationshipDomain_A5F3DD48B0FF55939033EE6E87AD3D53" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueHedgingMember" xlink:label="loc_us-gaap_FairValueHedgingMember_82B7C12A41C45BA08178F68D2C118791" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HedgingRelationshipDomain_A5F3DD48B0FF55939033EE6E87AD3D53" xlink:to="loc_us-gaap_FairValueHedgingMember_82B7C12A41C45BA08178F68D2C118791" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BalanceSheetLocationAxis" xlink:label="loc_us-gaap_BalanceSheetLocationAxis_CFA2406118C550A09114989128489722" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValuesDerivativesBalanceSheetLocationByDerivativeContractTypeByHedgingDesignationTable_203E902252675B57AA72CCB5135FE82B" xlink:to="loc_us-gaap_BalanceSheetLocationAxis_CFA2406118C550A09114989128489722" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BalanceSheetLocationDomain" xlink:label="loc_us-gaap_BalanceSheetLocationDomain_A99FFBFFE44A509A3F646D32971826D5_3639CE68F660501A8F4042849B1BEF0D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BalanceSheetLocationAxis_CFA2406118C550A09114989128489722" xlink:to="loc_us-gaap_BalanceSheetLocationDomain_A99FFBFFE44A509A3F646D32971826D5_3639CE68F660501A8F4042849B1BEF0D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BalanceSheetLocationDomain" xlink:label="loc_us-gaap_BalanceSheetLocationDomain_CA08CB7EA8C251FB9D18F7CEDB4C879A" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BalanceSheetLocationAxis_CFA2406118C550A09114989128489722" xlink:to="loc_us-gaap_BalanceSheetLocationDomain_CA08CB7EA8C251FB9D18F7CEDB4C879A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DerivativeFinancialInstrumentsLiabilitiesMember" xlink:label="loc_us-gaap_DerivativeFinancialInstrumentsLiabilitiesMember_03C290A86A95528C8680BBF1AA8AB128" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BalanceSheetLocationDomain_CA08CB7EA8C251FB9D18F7CEDB4C879A" xlink:to="loc_us-gaap_DerivativeFinancialInstrumentsLiabilitiesMember_03C290A86A95528C8680BBF1AA8AB128" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FinancialInstrumentAxis" xlink:label="loc_us-gaap_FinancialInstrumentAxis_4A5A3E185A6E54A8BF94C5973A247279" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValuesDerivativesBalanceSheetLocationByDerivativeContractTypeByHedgingDesignationTable_203E902252675B57AA72CCB5135FE82B" xlink:to="loc_us-gaap_FinancialInstrumentAxis_4A5A3E185A6E54A8BF94C5973A247279" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_907A84A710782BEA2E9C6D329719BBF1_3639CE68F660501A8F4042849B1BEF0D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_4A5A3E185A6E54A8BF94C5973A247279" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_907A84A710782BEA2E9C6D329719BBF1_3639CE68F660501A8F4042849B1BEF0D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_092B89FA1A245E2C98A8456382D24A5E" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_4A5A3E185A6E54A8BF94C5973A247279" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_092B89FA1A245E2C98A8456382D24A5E" xlink:type="arc" />
    <link:loc xlink:href="ucbi-20190930.xsd#ucbi_BrokeredCertificateOfDepositMember" xlink:label="loc_ucbi_BrokeredCertificateOfDepositMember_3D2A8EA459885E25A4312873D19DC697" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_092B89FA1A245E2C98A8456382D24A5E" xlink:to="loc_ucbi_BrokeredCertificateOfDepositMember_3D2A8EA459885E25A4312873D19DC697" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueHedgeLiabilitiesAtFairValue" xlink:label="loc_us-gaap_FairValueHedgeLiabilitiesAtFairValue_31A582C2E2B05ED09B6EB23E6FA97558" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativesFairValueLineItems_6FFAEC31935356F4A36669DCD3360023" xlink:to="loc_us-gaap_FairValueHedgeLiabilitiesAtFairValue_31A582C2E2B05ED09B6EB23E6FA97558" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://ucbi.com/role/DerivativesAndHedgingActivitiesDerivativesInFairValueHedgingRelationshipsDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DerivativeInstrumentsGainLossLineItems" xlink:label="loc_us-gaap_DerivativeInstrumentsGainLossLineItems_90C01A55DC3550BDA96B801DD88974B4" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable" xlink:label="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable_E2FEB95CC43E52FF9469CACEC6E9263D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossLineItems_90C01A55DC3550BDA96B801DD88974B4" xlink:to="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable_E2FEB95CC43E52FF9469CACEC6E9263D" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis" xlink:label="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_26F39177DAB2544B8B58509335F9D7B2" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable_E2FEB95CC43E52FF9469CACEC6E9263D" xlink:to="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_26F39177DAB2544B8B58509335F9D7B2" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_HedgingRelationshipDomain" xlink:label="loc_us-gaap_HedgingRelationshipDomain_7725B84B50F0ED8C97DEF747E584722E_3639CE68F660501A8F4042849B1BEF0D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_26F39177DAB2544B8B58509335F9D7B2" xlink:to="loc_us-gaap_HedgingRelationshipDomain_7725B84B50F0ED8C97DEF747E584722E_3639CE68F660501A8F4042849B1BEF0D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_HedgingRelationshipDomain" xlink:label="loc_us-gaap_HedgingRelationshipDomain_7E28E2E53D5E5A9AB9A90CCD46580AAB" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_26F39177DAB2544B8B58509335F9D7B2" xlink:to="loc_us-gaap_HedgingRelationshipDomain_7E28E2E53D5E5A9AB9A90CCD46580AAB" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueHedgingMember" xlink:label="loc_us-gaap_FairValueHedgingMember_9FC8C486FE0250DDA314EC567AC39CC8" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HedgingRelationshipDomain_7E28E2E53D5E5A9AB9A90CCD46580AAB" xlink:to="loc_us-gaap_FairValueHedgingMember_9FC8C486FE0250DDA314EC567AC39CC8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_IncomeStatementLocationAxis" xlink:label="loc_us-gaap_IncomeStatementLocationAxis_5CA97F5C0C2C5B4CAAF68BC11D829345" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable_E2FEB95CC43E52FF9469CACEC6E9263D" xlink:to="loc_us-gaap_IncomeStatementLocationAxis_5CA97F5C0C2C5B4CAAF68BC11D829345" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_IncomeStatementLocationDomain" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_ECE989DC207CDBABFB57F747E5851B4A_3639CE68F660501A8F4042849B1BEF0D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_5CA97F5C0C2C5B4CAAF68BC11D829345" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_ECE989DC207CDBABFB57F747E5851B4A_3639CE68F660501A8F4042849B1BEF0D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_IncomeStatementLocationDomain" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_1BFC5E4BAEF557C8B3DF871101122196" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_5CA97F5C0C2C5B4CAAF68BC11D829345" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_1BFC5E4BAEF557C8B3DF871101122196" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_InterestExpenseMember" xlink:label="loc_us-gaap_InterestExpenseMember_C0888A720BEA5BE8BECE5AC8FC149A20" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_1BFC5E4BAEF557C8B3DF871101122196" xlink:to="loc_us-gaap_InterestExpenseMember_C0888A720BEA5BE8BECE5AC8FC149A20" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_InterestIncomeMember" xlink:label="loc_us-gaap_InterestIncomeMember_9879B56AAB415C838848705F8146B20F" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_1BFC5E4BAEF557C8B3DF871101122196" xlink:to="loc_us-gaap_InterestIncomeMember_9879B56AAB415C838848705F8146B20F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FinancialInstrumentAxis" xlink:label="loc_us-gaap_FinancialInstrumentAxis_19604F83E6455F709FB7180E37803C4E" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable_E2FEB95CC43E52FF9469CACEC6E9263D" xlink:to="loc_us-gaap_FinancialInstrumentAxis_19604F83E6455F709FB7180E37803C4E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_4E9F0BEFEE293A630B2AF747E58635CA_3639CE68F660501A8F4042849B1BEF0D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_19604F83E6455F709FB7180E37803C4E" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_4E9F0BEFEE293A630B2AF747E58635CA_3639CE68F660501A8F4042849B1BEF0D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_6E2295961FC352F693BAF6DA44891D68" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_19604F83E6455F709FB7180E37803C4E" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_6E2295961FC352F693BAF6DA44891D68" xlink:type="arc" />
    <link:loc xlink:href="ucbi-20190930.xsd#ucbi_BrokeredCertificateOfDepositMember" xlink:label="loc_ucbi_BrokeredCertificateOfDepositMember_08D3205F63BB5F4AB88509C764FA0EFD" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_6E2295961FC352F693BAF6DA44891D68" xlink:to="loc_ucbi_BrokeredCertificateOfDepositMember_08D3205F63BB5F4AB88509C764FA0EFD" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CorporateBondSecuritiesMember" xlink:label="loc_us-gaap_CorporateBondSecuritiesMember_85F4AFBFEC5C5AD4802B6F1EE4ECCB22" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_6E2295961FC352F693BAF6DA44891D68" xlink:to="loc_us-gaap_CorporateBondSecuritiesMember_85F4AFBFEC5C5AD4802B6F1EE4ECCB22" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DerivativeGainLossOnDerivativeNetAbstract" xlink:label="loc_us-gaap_DerivativeGainLossOnDerivativeNetAbstract_D204C23FF5F75102BF917679A4ADC2B5" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossLineItems_90C01A55DC3550BDA96B801DD88974B4" xlink:to="loc_us-gaap_DerivativeGainLossOnDerivativeNetAbstract_D204C23FF5F75102BF917679A4ADC2B5" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ChangeInUnrealizedGainLossOnFairValueHedgingInstruments1" xlink:label="loc_us-gaap_ChangeInUnrealizedGainLossOnFairValueHedgingInstruments1_4CA31E6844FC50D2AAA048B77728ADD6" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeGainLossOnDerivativeNetAbstract_D204C23FF5F75102BF917679A4ADC2B5" xlink:to="loc_us-gaap_ChangeInUnrealizedGainLossOnFairValueHedgingInstruments1_4CA31E6844FC50D2AAA048B77728ADD6" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ChangeInUnrealizedGainLossOnHedgedItemInFairValueHedge1" xlink:label="loc_us-gaap_ChangeInUnrealizedGainLossOnHedgedItemInFairValueHedge1_A7CB20CAD507591595CC421953AF7ED8" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeGainLossOnDerivativeNetAbstract_D204C23FF5F75102BF917679A4ADC2B5" xlink:to="loc_us-gaap_ChangeInUnrealizedGainLossOnHedgedItemInFairValueHedge1_A7CB20CAD507591595CC421953AF7ED8" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://ucbi.com/role/DerivativesAndHedgingActivitiesDerivativesNotDesignatedAsHedgingInstrumentsDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DerivativesFairValueLineItems" xlink:label="loc_us-gaap_DerivativesFairValueLineItems_4E11BDF43847511A8D713C722FB5682E" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValuesDerivativesBalanceSheetLocationByDerivativeContractTypeByHedgingDesignationTable" xlink:label="loc_us-gaap_FairValuesDerivativesBalanceSheetLocationByDerivativeContractTypeByHedgingDesignationTable_DA0FC0F9095E538B8CA3BD932B40A572" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DerivativesFairValueLineItems_4E11BDF43847511A8D713C722FB5682E" xlink:to="loc_us-gaap_FairValuesDerivativesBalanceSheetLocationByDerivativeContractTypeByHedgingDesignationTable_DA0FC0F9095E538B8CA3BD932B40A572" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_HedgingDesignationAxis" xlink:label="loc_us-gaap_HedgingDesignationAxis_4E4C5B20FE4C563FA28E0FC3FF981E81" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValuesDerivativesBalanceSheetLocationByDerivativeContractTypeByHedgingDesignationTable_DA0FC0F9095E538B8CA3BD932B40A572" xlink:to="loc_us-gaap_HedgingDesignationAxis_4E4C5B20FE4C563FA28E0FC3FF981E81" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_HedgingDesignationDomain" xlink:label="loc_us-gaap_HedgingDesignationDomain_551E8CA9D48D8AC9BA236D32970E7B90_3639CE68F660501A8F4042849B1BEF0D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_HedgingDesignationAxis_4E4C5B20FE4C563FA28E0FC3FF981E81" xlink:to="loc_us-gaap_HedgingDesignationDomain_551E8CA9D48D8AC9BA236D32970E7B90_3639CE68F660501A8F4042849B1BEF0D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_HedgingDesignationDomain" xlink:label="loc_us-gaap_HedgingDesignationDomain_35C1F7992676555CAFC437A1FD8E82FB" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_HedgingDesignationAxis_4E4C5B20FE4C563FA28E0FC3FF981E81" xlink:to="loc_us-gaap_HedgingDesignationDomain_35C1F7992676555CAFC437A1FD8E82FB" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_NondesignatedMember" xlink:label="loc_us-gaap_NondesignatedMember_241ADD03BB0F576CAD59FAE26559A276" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HedgingDesignationDomain_35C1F7992676555CAFC437A1FD8E82FB" xlink:to="loc_us-gaap_NondesignatedMember_241ADD03BB0F576CAD59FAE26559A276" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BalanceSheetLocationAxis" xlink:label="loc_us-gaap_BalanceSheetLocationAxis_9D697D14A9E15802A7741C3858A6A617" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValuesDerivativesBalanceSheetLocationByDerivativeContractTypeByHedgingDesignationTable_DA0FC0F9095E538B8CA3BD932B40A572" xlink:to="loc_us-gaap_BalanceSheetLocationAxis_9D697D14A9E15802A7741C3858A6A617" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BalanceSheetLocationDomain" xlink:label="loc_us-gaap_BalanceSheetLocationDomain_DAA9DF9D9904674AACC56D32970FD6D9_3639CE68F660501A8F4042849B1BEF0D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BalanceSheetLocationAxis_9D697D14A9E15802A7741C3858A6A617" xlink:to="loc_us-gaap_BalanceSheetLocationDomain_DAA9DF9D9904674AACC56D32970FD6D9_3639CE68F660501A8F4042849B1BEF0D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BalanceSheetLocationDomain" xlink:label="loc_us-gaap_BalanceSheetLocationDomain_AFD96CB70C675540AA86B5B3417C01B8" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BalanceSheetLocationAxis_9D697D14A9E15802A7741C3858A6A617" xlink:to="loc_us-gaap_BalanceSheetLocationDomain_AFD96CB70C675540AA86B5B3417C01B8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DerivativeFinancialInstrumentsAssetsMember" xlink:label="loc_us-gaap_DerivativeFinancialInstrumentsAssetsMember_70F1DF328ACD5189B2B7E3D619FF1AB5" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BalanceSheetLocationDomain_AFD96CB70C675540AA86B5B3417C01B8" xlink:to="loc_us-gaap_DerivativeFinancialInstrumentsAssetsMember_70F1DF328ACD5189B2B7E3D619FF1AB5" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DerivativeFinancialInstrumentsLiabilitiesMember" xlink:label="loc_us-gaap_DerivativeFinancialInstrumentsLiabilitiesMember_497E7896626E500E829650A73B37DA6F" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BalanceSheetLocationDomain_AFD96CB70C675540AA86B5B3417C01B8" xlink:to="loc_us-gaap_DerivativeFinancialInstrumentsLiabilitiesMember_497E7896626E500E829650A73B37DA6F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DerivativeInstrumentRiskAxis" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_165FC27784005802A1D1A4F7DB2A5812" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValuesDerivativesBalanceSheetLocationByDerivativeContractTypeByHedgingDesignationTable_DA0FC0F9095E538B8CA3BD932B40A572" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_165FC27784005802A1D1A4F7DB2A5812" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DerivativeContractTypeDomain" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_86375144B2108B7CDFCF6D3297108F92_3639CE68F660501A8F4042849B1BEF0D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_165FC27784005802A1D1A4F7DB2A5812" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_86375144B2108B7CDFCF6D3297108F92_3639CE68F660501A8F4042849B1BEF0D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DerivativeContractTypeDomain" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_AA6234D9A6195366ACEFD35FD2DBD508" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_165FC27784005802A1D1A4F7DB2A5812" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_AA6234D9A6195366ACEFD35FD2DBD508" xlink:type="arc" />
    <link:loc xlink:href="ucbi-20190930.xsd#ucbi_CustomerSwapPositionMember" xlink:label="loc_ucbi_CustomerSwapPositionMember_62C3376963F1588AA7F0C0950821CF5F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_AA6234D9A6195366ACEFD35FD2DBD508" xlink:to="loc_ucbi_CustomerSwapPositionMember_62C3376963F1588AA7F0C0950821CF5F" xlink:type="arc" />
    <link:loc xlink:href="ucbi-20190930.xsd#ucbi_DealerOffsetToCustomerSwapPositionMember" xlink:label="loc_ucbi_DealerOffsetToCustomerSwapPositionMember_D4E80A3FB9C15116B16C8232D0157E5D" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_AA6234D9A6195366ACEFD35FD2DBD508" xlink:to="loc_ucbi_DealerOffsetToCustomerSwapPositionMember_D4E80A3FB9C15116B16C8232D0157E5D" xlink:type="arc" />
    <link:loc xlink:href="ucbi-20190930.xsd#ucbi_RiskParticipationsMember" xlink:label="loc_ucbi_RiskParticipationsMember_32B9C5B175D85BCE861FF823C2BC2CBF" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_AA6234D9A6195366ACEFD35FD2DBD508" xlink:to="loc_ucbi_RiskParticipationsMember_32B9C5B175D85BCE861FF823C2BC2CBF" xlink:type="arc" />
    <link:loc xlink:href="ucbi-20190930.xsd#ucbi_MortgageBankingLoanCommitmentMember" xlink:label="loc_ucbi_MortgageBankingLoanCommitmentMember_C54E9099A5AD5912825D22B6865BF148" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_AA6234D9A6195366ACEFD35FD2DBD508" xlink:to="loc_ucbi_MortgageBankingLoanCommitmentMember_C54E9099A5AD5912825D22B6865BF148" xlink:type="arc" />
    <link:loc xlink:href="ucbi-20190930.xsd#ucbi_MortgageBankingForwardSalesCommitmentMember" xlink:label="loc_ucbi_MortgageBankingForwardSalesCommitmentMember_EB415F0DA64A582A884D28918F8E2607" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_AA6234D9A6195366ACEFD35FD2DBD508" xlink:to="loc_ucbi_MortgageBankingForwardSalesCommitmentMember_EB415F0DA64A582A884D28918F8E2607" xlink:type="arc" />
    <link:loc xlink:href="ucbi-20190930.xsd#ucbi_BifurcatedEmbeddedDerivativeMember" xlink:label="loc_ucbi_BifurcatedEmbeddedDerivativeMember_87F146C73D8E56FCBDEB57B6D9B0BA9B" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_AA6234D9A6195366ACEFD35FD2DBD508" xlink:to="loc_ucbi_BifurcatedEmbeddedDerivativeMember_87F146C73D8E56FCBDEB57B6D9B0BA9B" xlink:type="arc" />
    <link:loc xlink:href="ucbi-20190930.xsd#ucbi_DealerOffsetsToBifurcatedEmbeddedDerivativesMember" xlink:label="loc_ucbi_DealerOffsetsToBifurcatedEmbeddedDerivativesMember_205C01156630552D8447A1690CA5DDFB" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_AA6234D9A6195366ACEFD35FD2DBD508" xlink:to="loc_ucbi_DealerOffsetsToBifurcatedEmbeddedDerivativesMember_205C01156630552D8447A1690CA5DDFB" xlink:type="arc" />
    <link:loc xlink:href="ucbi-20190930.xsd#ucbi_DeDesignatedCashFlowHedgeMember" xlink:label="loc_ucbi_DeDesignatedCashFlowHedgeMember_25C3C48233E35AC69CB7B74B1D0AEE0C" xlink:type="locator" />
    <link:definitionArc order="8" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_AA6234D9A6195366ACEFD35FD2DBD508" xlink:to="loc_ucbi_DeDesignatedCashFlowHedgeMember_25C3C48233E35AC69CB7B74B1D0AEE0C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_InterestRateDerivativeInstrumentsNotDesignatedAsHedgingInstrumentsAssetAtFairValue" xlink:label="loc_us-gaap_InterestRateDerivativeInstrumentsNotDesignatedAsHedgingInstrumentsAssetAtFairValue_43B4C300A25D5FCE8D75030633CA91EF" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativesFairValueLineItems_4E11BDF43847511A8D713C722FB5682E" xlink:to="loc_us-gaap_InterestRateDerivativeInstrumentsNotDesignatedAsHedgingInstrumentsAssetAtFairValue_43B4C300A25D5FCE8D75030633CA91EF" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_InterestRateDerivativeInstrumentsNotDesignatedAsHedgingInstrumentsLiabilityAtFairValue" xlink:label="loc_us-gaap_InterestRateDerivativeInstrumentsNotDesignatedAsHedgingInstrumentsLiabilityAtFairValue_0323BFC3820F5CE6B2F8626B4587456C" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativesFairValueLineItems_4E11BDF43847511A8D713C722FB5682E" xlink:to="loc_us-gaap_InterestRateDerivativeInstrumentsNotDesignatedAsHedgingInstrumentsLiabilityAtFairValue_0323BFC3820F5CE6B2F8626B4587456C" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://ucbi.com/role/DerivativesAndHedgingActivitiesGainsAndLossesRecognizedInIncomeOnDerivativesNotDesignatedAsHedgingInstrumentsDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DerivativeInstrumentsGainLossLineItems" xlink:label="loc_us-gaap_DerivativeInstrumentsGainLossLineItems_E1A695F29F595AAEAB6321473022C681" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable" xlink:label="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable_B5F1FBE4A99052B081670BB7EDB13AD6" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossLineItems_E1A695F29F595AAEAB6321473022C681" xlink:to="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable_B5F1FBE4A99052B081670BB7EDB13AD6" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_HedgingDesignationAxis" xlink:label="loc_us-gaap_HedgingDesignationAxis_859B644F7C695C9EAFB111F6B00D08BE" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable_B5F1FBE4A99052B081670BB7EDB13AD6" xlink:to="loc_us-gaap_HedgingDesignationAxis_859B644F7C695C9EAFB111F6B00D08BE" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_HedgingDesignationDomain" xlink:label="loc_us-gaap_HedgingDesignationDomain_78841B11FED82322ED906D3296F3A3B6_3639CE68F660501A8F4042849B1BEF0D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_HedgingDesignationAxis_859B644F7C695C9EAFB111F6B00D08BE" xlink:to="loc_us-gaap_HedgingDesignationDomain_78841B11FED82322ED906D3296F3A3B6_3639CE68F660501A8F4042849B1BEF0D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_HedgingDesignationDomain" xlink:label="loc_us-gaap_HedgingDesignationDomain_2677C326C2BA5ECBA29476D1534D5A83" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_HedgingDesignationAxis_859B644F7C695C9EAFB111F6B00D08BE" xlink:to="loc_us-gaap_HedgingDesignationDomain_2677C326C2BA5ECBA29476D1534D5A83" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_NondesignatedMember" xlink:label="loc_us-gaap_NondesignatedMember_63EC67212C1350F991C752EB81E76563" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HedgingDesignationDomain_2677C326C2BA5ECBA29476D1534D5A83" xlink:to="loc_us-gaap_NondesignatedMember_63EC67212C1350F991C752EB81E76563" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DerivativeInstrumentRiskAxis" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_CCCDFB8F074654A898E7ADD9D316BB4B" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable_B5F1FBE4A99052B081670BB7EDB13AD6" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_CCCDFB8F074654A898E7ADD9D316BB4B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DerivativeContractTypeDomain" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_9AB04ACAFF5437E4B90C6D3296F3CA92_3639CE68F660501A8F4042849B1BEF0D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_CCCDFB8F074654A898E7ADD9D316BB4B" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_9AB04ACAFF5437E4B90C6D3296F3CA92_3639CE68F660501A8F4042849B1BEF0D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DerivativeContractTypeDomain" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_47EE5E3A00D5562DB4FB636FE9D9F6C3" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_CCCDFB8F074654A898E7ADD9D316BB4B" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_47EE5E3A00D5562DB4FB636FE9D9F6C3" xlink:type="arc" />
    <link:loc xlink:href="ucbi-20190930.xsd#ucbi_CustomerDerivativesAndDealerOffsetsMember" xlink:label="loc_ucbi_CustomerDerivativesAndDealerOffsetsMember_E4D0A9060A2C5B06B06A589FC894BF13" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_47EE5E3A00D5562DB4FB636FE9D9F6C3" xlink:to="loc_ucbi_CustomerDerivativesAndDealerOffsetsMember_E4D0A9060A2C5B06B06A589FC894BF13" xlink:type="arc" />
    <link:loc xlink:href="ucbi-20190930.xsd#ucbi_BifurcatedEmbeddedDerivativesAndDealerOffsetsMember" xlink:label="loc_ucbi_BifurcatedEmbeddedDerivativesAndDealerOffsetsMember_D8BCBCE5C11C533EAEA54F90A452801D" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_47EE5E3A00D5562DB4FB636FE9D9F6C3" xlink:to="loc_ucbi_BifurcatedEmbeddedDerivativesAndDealerOffsetsMember_D8BCBCE5C11C533EAEA54F90A452801D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_InterestRateCapMember" xlink:label="loc_us-gaap_InterestRateCapMember_43D8B5A20EBC50CA86976038BBAB11ED" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_47EE5E3A00D5562DB4FB636FE9D9F6C3" xlink:to="loc_us-gaap_InterestRateCapMember_43D8B5A20EBC50CA86976038BBAB11ED" xlink:type="arc" />
    <link:loc xlink:href="ucbi-20190930.xsd#ucbi_DeDesignatedCashFlowHedgeMember" xlink:label="loc_ucbi_DeDesignatedCashFlowHedgeMember_96AF2F483A7D53BEADAF2D493E4D286F" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_47EE5E3A00D5562DB4FB636FE9D9F6C3" xlink:to="loc_ucbi_DeDesignatedCashFlowHedgeMember_96AF2F483A7D53BEADAF2D493E4D286F" xlink:type="arc" />
    <link:loc xlink:href="ucbi-20190930.xsd#ucbi_MortgageBankingDerivativesMember" xlink:label="loc_ucbi_MortgageBankingDerivativesMember_9D12321BC443515DA5FB228B84395BFA" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_47EE5E3A00D5562DB4FB636FE9D9F6C3" xlink:to="loc_ucbi_MortgageBankingDerivativesMember_9D12321BC443515DA5FB228B84395BFA" xlink:type="arc" />
    <link:loc xlink:href="ucbi-20190930.xsd#ucbi_RiskParticipationsMember" xlink:label="loc_ucbi_RiskParticipationsMember_6071102D699A52F59852F8F85E1CC94F" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_47EE5E3A00D5562DB4FB636FE9D9F6C3" xlink:to="loc_ucbi_RiskParticipationsMember_6071102D699A52F59852F8F85E1CC94F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_IncomeStatementLocationAxis" xlink:label="loc_us-gaap_IncomeStatementLocationAxis_63087877AE7C525384ACFF86D537C6D4" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable_B5F1FBE4A99052B081670BB7EDB13AD6" xlink:to="loc_us-gaap_IncomeStatementLocationAxis_63087877AE7C525384ACFF86D537C6D4" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_IncomeStatementLocationDomain" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_1162297416910911E71F6D3296F5FF3E_3639CE68F660501A8F4042849B1BEF0D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_63087877AE7C525384ACFF86D537C6D4" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_1162297416910911E71F6D3296F5FF3E_3639CE68F660501A8F4042849B1BEF0D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_IncomeStatementLocationDomain" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_F1DC21E692A850DAAA6B1FC2367105BA" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_63087877AE7C525384ACFF86D537C6D4" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_F1DC21E692A850DAAA6B1FC2367105BA" xlink:type="arc" />
    <link:loc xlink:href="ucbi-20190930.xsd#ucbi_OtherNoninterestIncomeMember" xlink:label="loc_ucbi_OtherNoninterestIncomeMember_7820619646035230AACB673349867817" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_F1DC21E692A850DAAA6B1FC2367105BA" xlink:to="loc_ucbi_OtherNoninterestIncomeMember_7820619646035230AACB673349867817" xlink:type="arc" />
    <link:loc xlink:href="ucbi-20190930.xsd#ucbi_MortgageLoanRevenueMember" xlink:label="loc_ucbi_MortgageLoanRevenueMember_1D7807CD5B995B3CB7FB6E4458890D0B" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_F1DC21E692A850DAAA6B1FC2367105BA" xlink:to="loc_ucbi_MortgageLoanRevenueMember_1D7807CD5B995B3CB7FB6E4458890D0B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DerivativeGainLossOnDerivativeNet" xlink:label="loc_us-gaap_DerivativeGainLossOnDerivativeNet_21582A1991E95E01BCF20B7B78221C1E" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossLineItems_E1A695F29F595AAEAB6321473022C681" xlink:to="loc_us-gaap_DerivativeGainLossOnDerivativeNet_21582A1991E95E01BCF20B7B78221C1E" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://ucbi.com/role/DerivativesAndHedgingActivitiesNarrativeDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DerivativeInstrumentsGainLossLineItems" xlink:label="loc_us-gaap_DerivativeInstrumentsGainLossLineItems_84D093FE1ABBF058CA1739D3E83CCD6B" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable" xlink:label="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable_5C6F2A6797F2A7A28A8239D3E838A8A0" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossLineItems_84D093FE1ABBF058CA1739D3E83CCD6B" xlink:to="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable_5C6F2A6797F2A7A28A8239D3E838A8A0" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_HedgingDesignationAxis" xlink:label="loc_us-gaap_HedgingDesignationAxis_898DAE5A45C039F1137839D3E838AEF8" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable_5C6F2A6797F2A7A28A8239D3E838A8A0" xlink:to="loc_us-gaap_HedgingDesignationAxis_898DAE5A45C039F1137839D3E838AEF8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_HedgingDesignationDomain" xlink:label="loc_us-gaap_HedgingDesignationDomain_2D12D51FB7E6E718A79839D3E83815D1_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_HedgingDesignationAxis_898DAE5A45C039F1137839D3E838AEF8" xlink:to="loc_us-gaap_HedgingDesignationDomain_2D12D51FB7E6E718A79839D3E83815D1_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_HedgingDesignationDomain" xlink:label="loc_us-gaap_HedgingDesignationDomain_2D12D51FB7E6E718A79839D3E83815D1" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_HedgingDesignationAxis_898DAE5A45C039F1137839D3E838AEF8" xlink:to="loc_us-gaap_HedgingDesignationDomain_2D12D51FB7E6E718A79839D3E83815D1" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_NotDesignatedAsHedgingInstrumentEconomicHedgeMember" xlink:label="loc_us-gaap_NotDesignatedAsHedgingInstrumentEconomicHedgeMember_4003EA276020DC335D2739D3E8380EB6" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HedgingDesignationDomain_2D12D51FB7E6E718A79839D3E83815D1" xlink:to="loc_us-gaap_NotDesignatedAsHedgingInstrumentEconomicHedgeMember_4003EA276020DC335D2739D3E8380EB6" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DerivativeInstrumentRiskAxis" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_CAAF5B9D9CFEDEC5D73939D3E8397C06" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable_5C6F2A6797F2A7A28A8239D3E838A8A0" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_CAAF5B9D9CFEDEC5D73939D3E8397C06" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DerivativeContractTypeDomain" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_0039FB917D8B4BBA470B39D3E83942BF_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_CAAF5B9D9CFEDEC5D73939D3E8397C06" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_0039FB917D8B4BBA470B39D3E83942BF_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DerivativeContractTypeDomain" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_0039FB917D8B4BBA470B39D3E83942BF" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_CAAF5B9D9CFEDEC5D73939D3E8397C06" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_0039FB917D8B4BBA470B39D3E83942BF" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_InterestRateSwapMember" xlink:label="loc_us-gaap_InterestRateSwapMember_124D2C140CADF3CC62E539D3E8397295" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_0039FB917D8B4BBA470B39D3E83942BF" xlink:to="loc_us-gaap_InterestRateSwapMember_124D2C140CADF3CC62E539D3E8397295" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_InterestRateCapMember" xlink:label="loc_us-gaap_InterestRateCapMember_A17F3A2E7CB26339F0A039D3E8395CC3" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_0039FB917D8B4BBA470B39D3E83942BF" xlink:to="loc_us-gaap_InterestRateCapMember_A17F3A2E7CB26339F0A039D3E8395CC3" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis" xlink:label="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_C6146752A457AD105A8139D3E83A6463" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable_5C6F2A6797F2A7A28A8239D3E838A8A0" xlink:to="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_C6146752A457AD105A8139D3E83A6463" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_HedgingRelationshipDomain" xlink:label="loc_us-gaap_HedgingRelationshipDomain_D6532531949044FCD9E939D3E83AC369_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_C6146752A457AD105A8139D3E83A6463" xlink:to="loc_us-gaap_HedgingRelationshipDomain_D6532531949044FCD9E939D3E83AC369_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_HedgingRelationshipDomain" xlink:label="loc_us-gaap_HedgingRelationshipDomain_D6532531949044FCD9E939D3E83AC369" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_C6146752A457AD105A8139D3E83A6463" xlink:to="loc_us-gaap_HedgingRelationshipDomain_D6532531949044FCD9E939D3E83AC369" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueHedgingMember" xlink:label="loc_us-gaap_FairValueHedgingMember_151CDA7D3983FF196C6539D3E83A9D99" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HedgingRelationshipDomain_D6532531949044FCD9E939D3E83AC369" xlink:to="loc_us-gaap_FairValueHedgingMember_151CDA7D3983FF196C6539D3E83A9D99" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_IncomeStatementLocationAxis" xlink:label="loc_us-gaap_IncomeStatementLocationAxis_6FCEDD958B816F9FF06439D3E83A2202" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable_5C6F2A6797F2A7A28A8239D3E838A8A0" xlink:to="loc_us-gaap_IncomeStatementLocationAxis_6FCEDD958B816F9FF06439D3E83A2202" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_IncomeStatementLocationDomain" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_20F072155888350F460639D3E83A80EB_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_6FCEDD958B816F9FF06439D3E83A2202" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_20F072155888350F460639D3E83A80EB_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_IncomeStatementLocationDomain" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_20F072155888350F460639D3E83A80EB" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_6FCEDD958B816F9FF06439D3E83A2202" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_20F072155888350F460639D3E83A80EB" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_InterestExpenseMember" xlink:label="loc_us-gaap_InterestExpenseMember_86A9B7D6BF74AD07E75F39D3E83BB39A" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_20F072155888350F460639D3E83A80EB" xlink:to="loc_us-gaap_InterestExpenseMember_86A9B7D6BF74AD07E75F39D3E83BB39A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_InterestIncomeMember" xlink:label="loc_us-gaap_InterestIncomeMember_2FF218EF9BBFAA41FEB739D3E83B133C" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_20F072155888350F460639D3E83A80EB" xlink:to="loc_us-gaap_InterestIncomeMember_2FF218EF9BBFAA41FEB739D3E83B133C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BalanceSheetLocationAxis" xlink:label="loc_us-gaap_BalanceSheetLocationAxis_DF84C3E5C8FAD9A010A639D3E83BDC24" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable_5C6F2A6797F2A7A28A8239D3E838A8A0" xlink:to="loc_us-gaap_BalanceSheetLocationAxis_DF84C3E5C8FAD9A010A639D3E83BDC24" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BalanceSheetLocationDomain" xlink:label="loc_us-gaap_BalanceSheetLocationDomain_CEC120E9CBA932E2965939D3E83B6427_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BalanceSheetLocationAxis_DF84C3E5C8FAD9A010A639D3E83BDC24" xlink:to="loc_us-gaap_BalanceSheetLocationDomain_CEC120E9CBA932E2965939D3E83B6427_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BalanceSheetLocationDomain" xlink:label="loc_us-gaap_BalanceSheetLocationDomain_CEC120E9CBA932E2965939D3E83B6427" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BalanceSheetLocationAxis_DF84C3E5C8FAD9A010A639D3E83BDC24" xlink:to="loc_us-gaap_BalanceSheetLocationDomain_CEC120E9CBA932E2965939D3E83B6427" xlink:type="arc" />
    <link:loc xlink:href="ucbi-20190930.xsd#ucbi_BrokeredDepositLiabilityMember" xlink:label="loc_ucbi_BrokeredDepositLiabilityMember_21D2AD4FC9301061451339D3E83B784D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BalanceSheetLocationDomain_CEC120E9CBA932E2965939D3E83B6427" xlink:to="loc_ucbi_BrokeredDepositLiabilityMember_21D2AD4FC9301061451339D3E83B784D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_NumberOfInterestRateDerivativesHeld" xlink:label="loc_us-gaap_NumberOfInterestRateDerivativesHeld_D376118975688049987039D3E83C7435" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossLineItems_84D093FE1ABBF058CA1739D3E83CCD6B" xlink:to="loc_us-gaap_NumberOfInterestRateDerivativesHeld_D376118975688049987039D3E83C7435" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DerivativeAssetNotionalAmount" xlink:label="loc_us-gaap_DerivativeAssetNotionalAmount_22D357C63DEB31E098BC39D3E83CA379" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossLineItems_84D093FE1ABBF058CA1739D3E83CCD6B" xlink:to="loc_us-gaap_DerivativeAssetNotionalAmount_22D357C63DEB31E098BC39D3E83CA379" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_HedgedLiabilityFairValueHedge" xlink:label="loc_us-gaap_HedgedLiabilityFairValueHedge_FA775A972A38D0F4C04539D3E83C2DA7" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossLineItems_84D093FE1ABBF058CA1739D3E83CCD6B" xlink:to="loc_us-gaap_HedgedLiabilityFairValueHedge_FA775A972A38D0F4C04539D3E83C2DA7" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_HedgedLiabilityFairValueHedgeCumulativeIncreaseDecrease" xlink:label="loc_us-gaap_HedgedLiabilityFairValueHedgeCumulativeIncreaseDecrease_164B033527A31D3DF2AE39D3E83D7E61" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossLineItems_84D093FE1ABBF058CA1739D3E83CCD6B" xlink:to="loc_us-gaap_HedgedLiabilityFairValueHedgeCumulativeIncreaseDecrease_164B033527A31D3DF2AE39D3E83D7E61" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DerivativeGainLossOnDerivativeNet" xlink:label="loc_us-gaap_DerivativeGainLossOnDerivativeNet_357008B443D60F76601B39D3E83D8A7E" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossLineItems_84D093FE1ABBF058CA1739D3E83CCD6B" xlink:to="loc_us-gaap_DerivativeGainLossOnDerivativeNet_357008B443D60F76601B39D3E83D8A7E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CollateralAlreadyPostedAggregateFairValue" xlink:label="loc_us-gaap_CollateralAlreadyPostedAggregateFairValue_FCB52BC9A351DED07BE339D3E83D089D" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossLineItems_84D093FE1ABBF058CA1739D3E83CCD6B" xlink:to="loc_us-gaap_CollateralAlreadyPostedAggregateFairValue_FCB52BC9A351DED07BE339D3E83D089D" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://ucbi.com/role/DerivativesAndHedgingActivitiesTables" xlink:type="extended" />
  <link:definitionLink xlink:role="http://ucbi.com/role/EarningsPerShare" xlink:type="extended" />
  <link:definitionLink xlink:role="http://ucbi.com/role/EarningsPerShareComputationOfBasicAndDilutedEarningsPerShareDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_07749B39CB415CA58C46C4935892C9B0" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_3192D4994B8E5A1E9F118B4640F07AF5" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_07749B39CB415CA58C46C4935892C9B0" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_3192D4994B8E5A1E9F118B4640F07AF5" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AwardTypeAxis" xlink:label="loc_us-gaap_AwardTypeAxis_E4A057463EF15EA39ADD455CEC1E8057" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_3192D4994B8E5A1E9F118B4640F07AF5" xlink:to="loc_us-gaap_AwardTypeAxis_E4A057463EF15EA39ADD455CEC1E8057" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_EFBA1439A24004F41FA5722177250271_3639CE68F660501A8F4042849B1BEF0D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_E4A057463EF15EA39ADD455CEC1E8057" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_EFBA1439A24004F41FA5722177250271_3639CE68F660501A8F4042849B1BEF0D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_C17E02F97BFB56FD854397FA2FBE8EB3" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_E4A057463EF15EA39ADD455CEC1E8057" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_C17E02F97BFB56FD854397FA2FBE8EB3" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_EmployeeStockOptionMember" xlink:label="loc_us-gaap_EmployeeStockOptionMember_C31ABBE479EC58E084E6D2CDB790A60F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_C17E02F97BFB56FD854397FA2FBE8EB3" xlink:to="loc_us-gaap_EmployeeStockOptionMember_C31ABBE479EC58E084E6D2CDB790A60F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RestrictedStockUnitsRSUMember" xlink:label="loc_us-gaap_RestrictedStockUnitsRSUMember_D290BB4195BF530480A0022BDC198FB8" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_C17E02F97BFB56FD854397FA2FBE8EB3" xlink:to="loc_us-gaap_RestrictedStockUnitsRSUMember_D290BB4195BF530480A0022BDC198FB8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_WeightedAverageNumberOfSharesOutstandingDilutedDisclosureItemsAbstract" xlink:label="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingDilutedDisclosureItemsAbstract_C53904A4CF675ADEA6000BD75F8006AA" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_07749B39CB415CA58C46C4935892C9B0" xlink:to="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingDilutedDisclosureItemsAbstract_C53904A4CF675ADEA6000BD75F8006AA" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_NetIncomeLoss" xlink:label="loc_us-gaap_NetIncomeLoss_F0C74792C4F45F918B2A18480FF5707E" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingDilutedDisclosureItemsAbstract_C53904A4CF675ADEA6000BD75F8006AA" xlink:to="loc_us-gaap_NetIncomeLoss_F0C74792C4F45F918B2A18480FF5707E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ParticipatingSecuritiesDistributedAndUndistributedEarningsLossBasic" xlink:label="loc_us-gaap_ParticipatingSecuritiesDistributedAndUndistributedEarningsLossBasic_85BC500D93CF544A9FF90C668C3DE588" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingDilutedDisclosureItemsAbstract_C53904A4CF675ADEA6000BD75F8006AA" xlink:to="loc_us-gaap_ParticipatingSecuritiesDistributedAndUndistributedEarningsLossBasic_85BC500D93CF544A9FF90C668C3DE588" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic" xlink:label="loc_us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic_99F645D39B615815AA55561712A3264D" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingDilutedDisclosureItemsAbstract_C53904A4CF675ADEA6000BD75F8006AA" xlink:to="loc_us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic_99F645D39B615815AA55561712A3264D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_WeightedAverageNumberOfSharesOutstandingAbstract" xlink:label="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingAbstract_A417306E245854BCA6006BC4B856B5ED" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingDilutedDisclosureItemsAbstract_C53904A4CF675ADEA6000BD75F8006AA" xlink:to="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingAbstract_A417306E245854BCA6006BC4B856B5ED" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_WeightedAverageNumberOfSharesOutstandingBasic" xlink:label="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_8D3F56D349015D5D9BA4E96211B69440" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingAbstract_A417306E245854BCA6006BC4B856B5ED" xlink:to="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_8D3F56D349015D5D9BA4E96211B69440" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DilutiveSecuritiesAbstract" xlink:label="loc_us-gaap_DilutiveSecuritiesAbstract_17153E8DCBFD5DEFB097BFC841278155" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingAbstract_A417306E245854BCA6006BC4B856B5ED" xlink:to="loc_us-gaap_DilutiveSecuritiesAbstract_17153E8DCBFD5DEFB097BFC841278155" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_IncrementalCommonSharesAttributableToShareBasedPaymentArrangements" xlink:label="loc_us-gaap_IncrementalCommonSharesAttributableToShareBasedPaymentArrangements_6C567665E5FD5A5F946803C803E8B9DB" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DilutiveSecuritiesAbstract_17153E8DCBFD5DEFB097BFC841278155" xlink:to="loc_us-gaap_IncrementalCommonSharesAttributableToShareBasedPaymentArrangements_6C567665E5FD5A5F946803C803E8B9DB" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding" xlink:label="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_DA3B86CE04D45ED0A8EDB5ED4292ED87" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingAbstract_A417306E245854BCA6006BC4B856B5ED" xlink:to="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_DA3B86CE04D45ED0A8EDB5ED4292ED87" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_EarningsPerShareBasicAndDilutedAbstract" xlink:label="loc_us-gaap_EarningsPerShareBasicAndDilutedAbstract_0034AC9C70935B9DB28C0597E3AC6515" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingDilutedDisclosureItemsAbstract_C53904A4CF675ADEA6000BD75F8006AA" xlink:to="loc_us-gaap_EarningsPerShareBasicAndDilutedAbstract_0034AC9C70935B9DB28C0597E3AC6515" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_EarningsPerShareBasic" xlink:label="loc_us-gaap_EarningsPerShareBasic_620573CD4B17535CA93346BF0366CE38" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareBasicAndDilutedAbstract_0034AC9C70935B9DB28C0597E3AC6515" xlink:to="loc_us-gaap_EarningsPerShareBasic_620573CD4B17535CA93346BF0366CE38" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_EarningsPerShareDiluted" xlink:label="loc_us-gaap_EarningsPerShareDiluted_212CE21C515F52D0B4F941598C1FB6DF" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareBasicAndDilutedAbstract_0034AC9C70935B9DB28C0597E3AC6515" xlink:to="loc_us-gaap_EarningsPerShareDiluted_212CE21C515F52D0B4F941598C1FB6DF" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://ucbi.com/role/EarningsPerShareNarrativeDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_13B94C6D6FE1B22B96A434EC8B1FD1D7" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable" xlink:label="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_E8CD3B7013684B68355534EC8B1E1335" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_13B94C6D6FE1B22B96A434EC8B1FD1D7" xlink:to="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_E8CD3B7013684B68355534EC8B1E1335" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_0349550A0908BEEF099834EC8B1E9482" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_E8CD3B7013684B68355534EC8B1E1335" xlink:to="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_0349550A0908BEEF099834EC8B1E9482" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AntidilutiveSecuritiesNameDomain" xlink:label="loc_us-gaap_AntidilutiveSecuritiesNameDomain_3A3319AABC74FE0EBD4E34EC8B1EF61E_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_0349550A0908BEEF099834EC8B1E9482" xlink:to="loc_us-gaap_AntidilutiveSecuritiesNameDomain_3A3319AABC74FE0EBD4E34EC8B1EF61E_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AntidilutiveSecuritiesNameDomain" xlink:label="loc_us-gaap_AntidilutiveSecuritiesNameDomain_3A3319AABC74FE0EBD4E34EC8B1EF61E" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_0349550A0908BEEF099834EC8B1E9482" xlink:to="loc_us-gaap_AntidilutiveSecuritiesNameDomain_3A3319AABC74FE0EBD4E34EC8B1EF61E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_EmployeeStockOptionMember" xlink:label="loc_us-gaap_EmployeeStockOptionMember_557D2EE15CDE6F90A3F334EC8B1FA70D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesNameDomain_3A3319AABC74FE0EBD4E34EC8B1EF61E" xlink:to="loc_us-gaap_EmployeeStockOptionMember_557D2EE15CDE6F90A3F334EC8B1FA70D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_WarrantMember" xlink:label="loc_us-gaap_WarrantMember_B94E4682DC1868ACDF5234EC8B1F17BD" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesNameDomain_3A3319AABC74FE0EBD4E34EC8B1EF61E" xlink:to="loc_us-gaap_WarrantMember_B94E4682DC1868ACDF5234EC8B1F17BD" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount_393E5355BC9DEAE7896834EC8B1FCFDD" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_13B94C6D6FE1B22B96A434EC8B1FD1D7" xlink:to="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount_393E5355BC9DEAE7896834EC8B1FCFDD" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice_3E283689EF309560567E34EC8B200A6D" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_13B94C6D6FE1B22B96A434EC8B1FD1D7" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice_3E283689EF309560567E34EC8B200A6D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1" xlink:label="loc_us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1_EAFF8C3B043BFF21329A34EC8B207904" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_13B94C6D6FE1B22B96A434EC8B1FD1D7" xlink:to="loc_us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1_EAFF8C3B043BFF21329A34EC8B207904" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://ucbi.com/role/EarningsPerShareTables" xlink:type="extended" />
  <link:definitionLink xlink:role="http://ucbi.com/role/GoodwillAndOtherIntangibleAssets" xlink:type="extended" />
  <link:definitionLink xlink:role="http://ucbi.com/role/GoodwillAndOtherIntangibleAssetsCarryingAmountDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsLineItems" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_14BF5ED9D2D95BA4B694C880C63BC040" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable" xlink:label="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_B4D54131BD595962AC550D643670EE58" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_14BF5ED9D2D95BA4B694C880C63BC040" xlink:to="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_B4D54131BD595962AC550D643670EE58" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_ABEC2B03B31E5945A5AA5CD828A102DC" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_B4D54131BD595962AC550D643670EE58" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_ABEC2B03B31E5945A5AA5CD828A102DC" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_60F26EBFC96A9612AC72F8CC4A70D4BA_3639CE68F660501A8F4042849B1BEF0D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_ABEC2B03B31E5945A5AA5CD828A102DC" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_60F26EBFC96A9612AC72F8CC4A70D4BA_3639CE68F660501A8F4042849B1BEF0D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_4CE6654E85C95BDE928D654979E663FB" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_ABEC2B03B31E5945A5AA5CD828A102DC" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_4CE6654E85C95BDE928D654979E663FB" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CoreDepositsMember" xlink:label="loc_us-gaap_CoreDepositsMember_79B3E3883DC05AB68D2E9CAB392FE8E0" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_4CE6654E85C95BDE928D654979E663FB" xlink:to="loc_us-gaap_CoreDepositsMember_79B3E3883DC05AB68D2E9CAB392FE8E0" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_NoncompeteAgreementsMember" xlink:label="loc_us-gaap_NoncompeteAgreementsMember_3710D3A11AFE5D64A0953760E83AC8AA" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_4CE6654E85C95BDE928D654979E663FB" xlink:to="loc_us-gaap_NoncompeteAgreementsMember_3710D3A11AFE5D64A0953760E83AC8AA" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_IntangibleAssetsGrossExcludingGoodwill" xlink:label="loc_us-gaap_IntangibleAssetsGrossExcludingGoodwill_BF01E102BBC6587890AF6A45EA83CB00" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_14BF5ED9D2D95BA4B694C880C63BC040" xlink:to="loc_us-gaap_IntangibleAssetsGrossExcludingGoodwill_BF01E102BBC6587890AF6A45EA83CB00" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization_51DADB5E96055287A114282957061BD6" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_14BF5ED9D2D95BA4B694C880C63BC040" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization_51DADB5E96055287A114282957061BD6" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsNet" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsNet_411E900EDA8755DDB121A61AAFD0E876" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_14BF5ED9D2D95BA4B694C880C63BC040" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsNet_411E900EDA8755DDB121A61AAFD0E876" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_Goodwill" xlink:label="loc_us-gaap_Goodwill_960AF229FB9B521EB6EEFE4EB386A2DF" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_14BF5ED9D2D95BA4B694C880C63BC040" xlink:to="loc_us-gaap_Goodwill_960AF229FB9B521EB6EEFE4EB386A2DF" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_IntangibleAssetsNetIncludingGoodwill" xlink:label="loc_us-gaap_IntangibleAssetsNetIncludingGoodwill_2B36062855E85789927C491ED42AA07E" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_14BF5ED9D2D95BA4B694C880C63BC040" xlink:to="loc_us-gaap_IntangibleAssetsNetIncludingGoodwill_2B36062855E85789927C491ED42AA07E" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://ucbi.com/role/GoodwillAndOtherIntangibleAssetsChangesInCarryingAmountOfGoodwillDetails" xlink:type="extended" />
  <link:definitionLink xlink:role="http://ucbi.com/role/GoodwillAndOtherIntangibleAssetsEstimatedAggregateAmortizationExpenseForFuturePeriodsDetails" xlink:type="extended" />
  <link:definitionLink xlink:role="http://ucbi.com/role/GoodwillAndOtherIntangibleAssetsTables" xlink:type="extended" />
  <link:definitionLink xlink:role="http://ucbi.com/role/IncomeTaxes" xlink:type="extended" />
  <link:definitionLink xlink:role="http://ucbi.com/role/IncomeTaxesNarrativeDetails" xlink:type="extended" />
  <link:definitionLink xlink:role="http://ucbi.com/role/LoansAndLeasesAndAllowanceForCreditLosses" xlink:type="extended" />
  <link:definitionLink xlink:role="http://ucbi.com/role/LoansAndLeasesAndAllowanceForCreditLossesAgingOfRecordedInvestmentInPastDueLoansDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FinancingReceivableRecordedInvestmentPastDueLineItems" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentPastDueLineItems_3EEDF812F4425A35A55D12294D86C0BB" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ScheduleOfFinancingReceivablesPastDueTable" xlink:label="loc_us-gaap_ScheduleOfFinancingReceivablesPastDueTable_3DBADC1F9E825868AC020AFF2B57D958" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentPastDueLineItems_3EEDF812F4425A35A55D12294D86C0BB" xlink:to="loc_us-gaap_ScheduleOfFinancingReceivablesPastDueTable_3DBADC1F9E825868AC020AFF2B57D958" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis" xlink:label="loc_us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis_5882A917D21D5DC49AE3DB0D1754E958" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFinancingReceivablesPastDueTable_3DBADC1F9E825868AC020AFF2B57D958" xlink:to="loc_us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis_5882A917D21D5DC49AE3DB0D1754E958" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ReceivableTypeDomain" xlink:label="loc_us-gaap_ReceivableTypeDomain_F405E69A080BDA6A15F1F747E3EFEF0C_3639CE68F660501A8F4042849B1BEF0D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis_5882A917D21D5DC49AE3DB0D1754E958" xlink:to="loc_us-gaap_ReceivableTypeDomain_F405E69A080BDA6A15F1F747E3EFEF0C_3639CE68F660501A8F4042849B1BEF0D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ReceivableTypeDomain" xlink:label="loc_us-gaap_ReceivableTypeDomain_02D066CC45AB50CDA27A97243F7A18A3" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis_5882A917D21D5DC49AE3DB0D1754E958" xlink:to="loc_us-gaap_ReceivableTypeDomain_02D066CC45AB50CDA27A97243F7A18A3" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LoansReceivableMember" xlink:label="loc_us-gaap_LoansReceivableMember_842F199719B653F684D4FA5C5383F9A6" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ReceivableTypeDomain_02D066CC45AB50CDA27A97243F7A18A3" xlink:to="loc_us-gaap_LoansReceivableMember_842F199719B653F684D4FA5C5383F9A6" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FinancingReceivablePortfolioSegmentAxis" xlink:label="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_25963DA24BCE56848F7C3C82920886D7" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFinancingReceivablesPastDueTable_3DBADC1F9E825868AC020AFF2B57D958" xlink:to="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_25963DA24BCE56848F7C3C82920886D7" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FinancingReceivablePortfolioSegmentDomain" xlink:label="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_0303903738A04FF5643FF747E3EF7E15_3639CE68F660501A8F4042849B1BEF0D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_25963DA24BCE56848F7C3C82920886D7" xlink:to="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_0303903738A04FF5643FF747E3EF7E15_3639CE68F660501A8F4042849B1BEF0D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FinancingReceivablePortfolioSegmentDomain" xlink:label="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_A8F616A3AA3E516782F204B9E2039590" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_25963DA24BCE56848F7C3C82920886D7" xlink:to="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_A8F616A3AA3E516782F204B9E2039590" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CommercialPortfolioSegmentMember" xlink:label="loc_us-gaap_CommercialPortfolioSegmentMember_8BE6B4788C9055A196E0CA580D853A32" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_A8F616A3AA3E516782F204B9E2039590" xlink:to="loc_us-gaap_CommercialPortfolioSegmentMember_8BE6B4788C9055A196E0CA580D853A32" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ResidentialPortfolioSegmentMember" xlink:label="loc_us-gaap_ResidentialPortfolioSegmentMember_8CE0DD0D0D6354938ED9ACFD9343E98E" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_A8F616A3AA3E516782F204B9E2039590" xlink:to="loc_us-gaap_ResidentialPortfolioSegmentMember_8CE0DD0D0D6354938ED9ACFD9343E98E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ConsumerPortfolioSegmentMember" xlink:label="loc_us-gaap_ConsumerPortfolioSegmentMember_7749FD2E12FA582C8CBC08EF4DC92F6F" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_A8F616A3AA3E516782F204B9E2039590" xlink:to="loc_us-gaap_ConsumerPortfolioSegmentMember_7749FD2E12FA582C8CBC08EF4DC92F6F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_8429369B80915F209B460D034B71C50F" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFinancingReceivablesPastDueTable_3DBADC1F9E825868AC020AFF2B57D958" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_8429369B80915F209B460D034B71C50F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_E3F2ED35C11764078D5CF747E3F0B143_3639CE68F660501A8F4042849B1BEF0D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_8429369B80915F209B460D034B71C50F" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_E3F2ED35C11764078D5CF747E3F0B143_3639CE68F660501A8F4042849B1BEF0D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_C05F9724BF5B5D18A672CD1304334799" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_8429369B80915F209B460D034B71C50F" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_C05F9724BF5B5D18A672CD1304334799" xlink:type="arc" />
    <link:loc xlink:href="ucbi-20190930.xsd#ucbi_OwnerOccupiedCommercialRealEstateMember" xlink:label="loc_ucbi_OwnerOccupiedCommercialRealEstateMember_8840E0CD0710546CAD806016E77002E9" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_C05F9724BF5B5D18A672CD1304334799" xlink:to="loc_ucbi_OwnerOccupiedCommercialRealEstateMember_8840E0CD0710546CAD806016E77002E9" xlink:type="arc" />
    <link:loc xlink:href="ucbi-20190930.xsd#ucbi_IncomeProducingCommercialRealEstateMember" xlink:label="loc_ucbi_IncomeProducingCommercialRealEstateMember_94A841AB723D5A808A8C457E4D9D7D8D" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_C05F9724BF5B5D18A672CD1304334799" xlink:to="loc_ucbi_IncomeProducingCommercialRealEstateMember_94A841AB723D5A808A8C457E4D9D7D8D" xlink:type="arc" />
    <link:loc xlink:href="ucbi-20190930.xsd#ucbi_CommercialAndIndustrialClassificationMember" xlink:label="loc_ucbi_CommercialAndIndustrialClassificationMember_4048194AF0085AC9911C2A08CAE6D5C3" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_C05F9724BF5B5D18A672CD1304334799" xlink:to="loc_ucbi_CommercialAndIndustrialClassificationMember_4048194AF0085AC9911C2A08CAE6D5C3" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ConstructionLoansMember" xlink:label="loc_us-gaap_ConstructionLoansMember_240A042476E95DAA841937AE75AF478A" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_C05F9724BF5B5D18A672CD1304334799" xlink:to="loc_us-gaap_ConstructionLoansMember_240A042476E95DAA841937AE75AF478A" xlink:type="arc" />
    <link:loc xlink:href="ucbi-20190930.xsd#ucbi_EquipmentFinancingMember" xlink:label="loc_ucbi_EquipmentFinancingMember_FDAE5D270CAD51E5B554326563C286D6" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_C05F9724BF5B5D18A672CD1304334799" xlink:to="loc_ucbi_EquipmentFinancingMember_FDAE5D270CAD51E5B554326563C286D6" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ResidentialMortgageMember" xlink:label="loc_us-gaap_ResidentialMortgageMember_2B5D90EB9A485C1FBA0E0444B7500D48" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_C05F9724BF5B5D18A672CD1304334799" xlink:to="loc_us-gaap_ResidentialMortgageMember_2B5D90EB9A485C1FBA0E0444B7500D48" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_HomeEquityMember" xlink:label="loc_us-gaap_HomeEquityMember_998715A65C0F5F00B97FC22CF80A4BA2" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_C05F9724BF5B5D18A672CD1304334799" xlink:to="loc_us-gaap_HomeEquityMember_998715A65C0F5F00B97FC22CF80A4BA2" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AutomobileLoanMember" xlink:label="loc_us-gaap_AutomobileLoanMember_CC147302466C580B824F595A18646D37" xlink:type="locator" />
    <link:definitionArc order="8" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_C05F9724BF5B5D18A672CD1304334799" xlink:to="loc_us-gaap_AutomobileLoanMember_CC147302466C580B824F595A18646D37" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FinancingReceivablesPeriodPastDueAxis" xlink:label="loc_us-gaap_FinancingReceivablesPeriodPastDueAxis_0FDB5D1D08625ED7B926864646E6F447" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFinancingReceivablesPastDueTable_3DBADC1F9E825868AC020AFF2B57D958" xlink:to="loc_us-gaap_FinancingReceivablesPeriodPastDueAxis_0FDB5D1D08625ED7B926864646E6F447" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FinancingReceivablesPeriodPastDueDomain" xlink:label="loc_us-gaap_FinancingReceivablesPeriodPastDueDomain_34667BAD48D5BE33CBDAF747E3F21597_3639CE68F660501A8F4042849B1BEF0D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancingReceivablesPeriodPastDueAxis_0FDB5D1D08625ED7B926864646E6F447" xlink:to="loc_us-gaap_FinancingReceivablesPeriodPastDueDomain_34667BAD48D5BE33CBDAF747E3F21597_3639CE68F660501A8F4042849B1BEF0D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FinancingReceivablesPeriodPastDueDomain" xlink:label="loc_us-gaap_FinancingReceivablesPeriodPastDueDomain_15177300AA30569EAF33AC0FE4940987" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancingReceivablesPeriodPastDueAxis_0FDB5D1D08625ED7B926864646E6F447" xlink:to="loc_us-gaap_FinancingReceivablesPeriodPastDueDomain_15177300AA30569EAF33AC0FE4940987" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FinancingReceivables30To59DaysPastDueMember" xlink:label="loc_us-gaap_FinancingReceivables30To59DaysPastDueMember_81E9AED4AFF85653976CAB9F20AC65B5" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivablesPeriodPastDueDomain_15177300AA30569EAF33AC0FE4940987" xlink:to="loc_us-gaap_FinancingReceivables30To59DaysPastDueMember_81E9AED4AFF85653976CAB9F20AC65B5" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FinancingReceivables60To89DaysPastDueMember" xlink:label="loc_us-gaap_FinancingReceivables60To89DaysPastDueMember_6B379315873D55B697FCBA5EFFB4E8DD" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivablesPeriodPastDueDomain_15177300AA30569EAF33AC0FE4940987" xlink:to="loc_us-gaap_FinancingReceivables60To89DaysPastDueMember_6B379315873D55B697FCBA5EFFB4E8DD" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FinancingReceivablesEqualToGreaterThan90DaysPastDueMember" xlink:label="loc_us-gaap_FinancingReceivablesEqualToGreaterThan90DaysPastDueMember_28B8D82F603751A29338BFAF5F869853" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivablesPeriodPastDueDomain_15177300AA30569EAF33AC0FE4940987" xlink:to="loc_us-gaap_FinancingReceivablesEqualToGreaterThan90DaysPastDueMember_28B8D82F603751A29338BFAF5F869853" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FinancingReceivableRecordedInvestmentAgingAbstract" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentAgingAbstract_17979029A64250F099FEDA88C4FDEF94" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentPastDueLineItems_3EEDF812F4425A35A55D12294D86C0BB" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentAgingAbstract_17979029A64250F099FEDA88C4FDEF94" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FinancingReceivableRecordedInvestmentPastDue" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentPastDue_70681DC1962E5F7C8AD908CC64720870" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentAgingAbstract_17979029A64250F099FEDA88C4FDEF94" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentPastDue_70681DC1962E5F7C8AD908CC64720870" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FinancingReceivableRecordedInvestmentCurrent" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentCurrent_696BED5DEC5354CD90E84AC27C07345A" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentAgingAbstract_17979029A64250F099FEDA88C4FDEF94" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentCurrent_696BED5DEC5354CD90E84AC27C07345A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CertainLoansAcquiredInTransferNotAccountedForAsDebtSecuritiesCarryingAmountNet" xlink:label="loc_us-gaap_CertainLoansAcquiredInTransferNotAccountedForAsDebtSecuritiesCarryingAmountNet_998F96A35E2F5E2A820F70BD391294E5" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentAgingAbstract_17979029A64250F099FEDA88C4FDEF94" xlink:to="loc_us-gaap_CertainLoansAcquiredInTransferNotAccountedForAsDebtSecuritiesCarryingAmountNet_998F96A35E2F5E2A820F70BD391294E5" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome" xlink:label="loc_us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome_C7599619DD3E5E379F2E21834A86BC94" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentAgingAbstract_17979029A64250F099FEDA88C4FDEF94" xlink:to="loc_us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome_C7599619DD3E5E379F2E21834A86BC94" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://ucbi.com/role/LoansAndLeasesAndAllowanceForCreditLossesAverageBalancesOfImpairedLoansAndIncomeRecognizedOnImpairedLoansDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FinancingReceivableAllowanceForCreditLossesLineItems" xlink:label="loc_us-gaap_FinancingReceivableAllowanceForCreditLossesLineItems_9DC102927D7A5AB488D967C372A8DA4F" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ScheduleOfFinancingReceivableAllowanceForCreditLossesTable" xlink:label="loc_us-gaap_ScheduleOfFinancingReceivableAllowanceForCreditLossesTable_C71C7D9BD38B566E8DE66D82F62427E4" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FinancingReceivableAllowanceForCreditLossesLineItems_9DC102927D7A5AB488D967C372A8DA4F" xlink:to="loc_us-gaap_ScheduleOfFinancingReceivableAllowanceForCreditLossesTable_C71C7D9BD38B566E8DE66D82F62427E4" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis" xlink:label="loc_us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis_2597A61F02AA58C4B4039F48758396CC" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFinancingReceivableAllowanceForCreditLossesTable_C71C7D9BD38B566E8DE66D82F62427E4" xlink:to="loc_us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis_2597A61F02AA58C4B4039F48758396CC" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ReceivableTypeDomain" xlink:label="loc_us-gaap_ReceivableTypeDomain_2C945FA3F63BA44F1A78F8CC4B8D6359_3639CE68F660501A8F4042849B1BEF0D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis_2597A61F02AA58C4B4039F48758396CC" xlink:to="loc_us-gaap_ReceivableTypeDomain_2C945FA3F63BA44F1A78F8CC4B8D6359_3639CE68F660501A8F4042849B1BEF0D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ReceivableTypeDomain" xlink:label="loc_us-gaap_ReceivableTypeDomain_99FAB04002F65FB29C99E7A1A01CA686" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis_2597A61F02AA58C4B4039F48758396CC" xlink:to="loc_us-gaap_ReceivableTypeDomain_99FAB04002F65FB29C99E7A1A01CA686" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LoansReceivableMember" xlink:label="loc_us-gaap_LoansReceivableMember_0BB695196EE95707AEDE0D59B72570CA" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ReceivableTypeDomain_99FAB04002F65FB29C99E7A1A01CA686" xlink:to="loc_us-gaap_LoansReceivableMember_0BB695196EE95707AEDE0D59B72570CA" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FinancingReceivablePortfolioSegmentAxis" xlink:label="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_AE13BFAAA222563CA61516C367997FBF" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFinancingReceivableAllowanceForCreditLossesTable_C71C7D9BD38B566E8DE66D82F62427E4" xlink:to="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_AE13BFAAA222563CA61516C367997FBF" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FinancingReceivablePortfolioSegmentDomain" xlink:label="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_2ED55A7AF3EB9223C030F8CC4B8E08A3_3639CE68F660501A8F4042849B1BEF0D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_AE13BFAAA222563CA61516C367997FBF" xlink:to="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_2ED55A7AF3EB9223C030F8CC4B8E08A3_3639CE68F660501A8F4042849B1BEF0D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FinancingReceivablePortfolioSegmentDomain" xlink:label="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_5A166E0AC33E548BAAA0D26BF55DC288" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_AE13BFAAA222563CA61516C367997FBF" xlink:to="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_5A166E0AC33E548BAAA0D26BF55DC288" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CommercialPortfolioSegmentMember" xlink:label="loc_us-gaap_CommercialPortfolioSegmentMember_0C06B9B617B858DE8C6241A90EE0288E" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_5A166E0AC33E548BAAA0D26BF55DC288" xlink:to="loc_us-gaap_CommercialPortfolioSegmentMember_0C06B9B617B858DE8C6241A90EE0288E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ResidentialPortfolioSegmentMember" xlink:label="loc_us-gaap_ResidentialPortfolioSegmentMember_B558BF3CF17156EFBDD9BD03E8CDBBD2" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_5A166E0AC33E548BAAA0D26BF55DC288" xlink:to="loc_us-gaap_ResidentialPortfolioSegmentMember_B558BF3CF17156EFBDD9BD03E8CDBBD2" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ConsumerPortfolioSegmentMember" xlink:label="loc_us-gaap_ConsumerPortfolioSegmentMember_A589F8F6CDA65775BADE3BFFFDE62910" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_5A166E0AC33E548BAAA0D26BF55DC288" xlink:to="loc_us-gaap_ConsumerPortfolioSegmentMember_A589F8F6CDA65775BADE3BFFFDE62910" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_C5999AED3317555786F7C128185742FF" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFinancingReceivableAllowanceForCreditLossesTable_C71C7D9BD38B566E8DE66D82F62427E4" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_C5999AED3317555786F7C128185742FF" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_AEE10567239D6FF3B48AF8CC4B8F1077_3639CE68F660501A8F4042849B1BEF0D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_C5999AED3317555786F7C128185742FF" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_AEE10567239D6FF3B48AF8CC4B8F1077_3639CE68F660501A8F4042849B1BEF0D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_5280E0E9B93D5B8CACB9F84BC7392F0F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_C5999AED3317555786F7C128185742FF" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_5280E0E9B93D5B8CACB9F84BC7392F0F" xlink:type="arc" />
    <link:loc xlink:href="ucbi-20190930.xsd#ucbi_OwnerOccupiedCommercialRealEstateMember" xlink:label="loc_ucbi_OwnerOccupiedCommercialRealEstateMember_9632CC8B8E5B53CB8FB0037DF9712337" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_5280E0E9B93D5B8CACB9F84BC7392F0F" xlink:to="loc_ucbi_OwnerOccupiedCommercialRealEstateMember_9632CC8B8E5B53CB8FB0037DF9712337" xlink:type="arc" />
    <link:loc xlink:href="ucbi-20190930.xsd#ucbi_IncomeProducingCommercialRealEstateMember" xlink:label="loc_ucbi_IncomeProducingCommercialRealEstateMember_1B16A0A2F89C523097A503989CD0AF39" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_5280E0E9B93D5B8CACB9F84BC7392F0F" xlink:to="loc_ucbi_IncomeProducingCommercialRealEstateMember_1B16A0A2F89C523097A503989CD0AF39" xlink:type="arc" />
    <link:loc xlink:href="ucbi-20190930.xsd#ucbi_CommercialAndIndustrialClassificationMember" xlink:label="loc_ucbi_CommercialAndIndustrialClassificationMember_76DC289B68905B7F9E892A87118B3011" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_5280E0E9B93D5B8CACB9F84BC7392F0F" xlink:to="loc_ucbi_CommercialAndIndustrialClassificationMember_76DC289B68905B7F9E892A87118B3011" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ConstructionLoansMember" xlink:label="loc_us-gaap_ConstructionLoansMember_C332DE92163B557A968336DA8F20F849" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_5280E0E9B93D5B8CACB9F84BC7392F0F" xlink:to="loc_us-gaap_ConstructionLoansMember_C332DE92163B557A968336DA8F20F849" xlink:type="arc" />
    <link:loc xlink:href="ucbi-20190930.xsd#ucbi_EquipmentFinancingMember" xlink:label="loc_ucbi_EquipmentFinancingMember_DA696EE0488E5C3F963DF955DE104EEE" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_5280E0E9B93D5B8CACB9F84BC7392F0F" xlink:to="loc_ucbi_EquipmentFinancingMember_DA696EE0488E5C3F963DF955DE104EEE" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ResidentialMortgageMember" xlink:label="loc_us-gaap_ResidentialMortgageMember_18051A0110735221908703FA0206FCFE" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_5280E0E9B93D5B8CACB9F84BC7392F0F" xlink:to="loc_us-gaap_ResidentialMortgageMember_18051A0110735221908703FA0206FCFE" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_HomeEquityMember" xlink:label="loc_us-gaap_HomeEquityMember_4AF7F3D2891D511DB1F1EA8DD3DF9B3E" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_5280E0E9B93D5B8CACB9F84BC7392F0F" xlink:to="loc_us-gaap_HomeEquityMember_4AF7F3D2891D511DB1F1EA8DD3DF9B3E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AutomobileLoanMember" xlink:label="loc_us-gaap_AutomobileLoanMember_C6DFBD3D01F0509DACAC70293912EAD3" xlink:type="locator" />
    <link:definitionArc order="8" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_5280E0E9B93D5B8CACB9F84BC7392F0F" xlink:to="loc_us-gaap_AutomobileLoanMember_C6DFBD3D01F0509DACAC70293912EAD3" xlink:type="arc" />
    <link:loc xlink:href="ucbi-20190930.xsd#ucbi_AverageBalancesOfImpairedLoansAndIncomeRecognizedOnImpairedLoansAbstract" xlink:label="loc_ucbi_AverageBalancesOfImpairedLoansAndIncomeRecognizedOnImpairedLoansAbstract_FF3480BB36E150948616162E134E593E" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableAllowanceForCreditLossesLineItems_9DC102927D7A5AB488D967C372A8DA4F" xlink:to="loc_ucbi_AverageBalancesOfImpairedLoansAndIncomeRecognizedOnImpairedLoansAbstract_FF3480BB36E150948616162E134E593E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ImpairedFinancingReceivableAverageRecordedInvestment" xlink:label="loc_us-gaap_ImpairedFinancingReceivableAverageRecordedInvestment_B2E49CD70C585D05B4D822EB92E9F47C" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ucbi_AverageBalancesOfImpairedLoansAndIncomeRecognizedOnImpairedLoansAbstract_FF3480BB36E150948616162E134E593E" xlink:to="loc_us-gaap_ImpairedFinancingReceivableAverageRecordedInvestment_B2E49CD70C585D05B4D822EB92E9F47C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ImpairedFinancingReceivableInterestIncomeAccrualMethod" xlink:label="loc_us-gaap_ImpairedFinancingReceivableInterestIncomeAccrualMethod_4F84DF5EC8165438A5CAFAB2B819E587" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ucbi_AverageBalancesOfImpairedLoansAndIncomeRecognizedOnImpairedLoansAbstract_FF3480BB36E150948616162E134E593E" xlink:to="loc_us-gaap_ImpairedFinancingReceivableInterestIncomeAccrualMethod_4F84DF5EC8165438A5CAFAB2B819E587" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ImpairedFinancingReceivableInterestIncomeCashBasisMethod" xlink:label="loc_us-gaap_ImpairedFinancingReceivableInterestIncomeCashBasisMethod_6B28D48F45A956E6BD2F87BDA274372B" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ucbi_AverageBalancesOfImpairedLoansAndIncomeRecognizedOnImpairedLoansAbstract_FF3480BB36E150948616162E134E593E" xlink:to="loc_us-gaap_ImpairedFinancingReceivableInterestIncomeCashBasisMethod_6B28D48F45A956E6BD2F87BDA274372B" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://ucbi.com/role/LoansAndLeasesAndAllowanceForCreditLossesBalanceAndActivityInAllowanceForLoanLossesByPortfolioSegmentAndRecordedInvestmentInLoansByPortfolioSegmentDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FinancingReceivableAllowanceForCreditLossesLineItems" xlink:label="loc_us-gaap_FinancingReceivableAllowanceForCreditLossesLineItems_00704E9273FE54A8A260DCECC5B3D655" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ScheduleOfFinancingReceivableAllowanceForCreditLossesTable" xlink:label="loc_us-gaap_ScheduleOfFinancingReceivableAllowanceForCreditLossesTable_CFDFB9D79A5B551DA7723B41B0C385DA" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FinancingReceivableAllowanceForCreditLossesLineItems_00704E9273FE54A8A260DCECC5B3D655" xlink:to="loc_us-gaap_ScheduleOfFinancingReceivableAllowanceForCreditLossesTable_CFDFB9D79A5B551DA7723B41B0C385DA" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis" xlink:label="loc_us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis_38879B2FA7E054DB8E8271C7830A050D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFinancingReceivableAllowanceForCreditLossesTable_CFDFB9D79A5B551DA7723B41B0C385DA" xlink:to="loc_us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis_38879B2FA7E054DB8E8271C7830A050D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ReceivableTypeDomain" xlink:label="loc_us-gaap_ReceivableTypeDomain_13486E0F722410EC5D75F786A6139A69_3639CE68F660501A8F4042849B1BEF0D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis_38879B2FA7E054DB8E8271C7830A050D" xlink:to="loc_us-gaap_ReceivableTypeDomain_13486E0F722410EC5D75F786A6139A69_3639CE68F660501A8F4042849B1BEF0D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ReceivableTypeDomain" xlink:label="loc_us-gaap_ReceivableTypeDomain_5581C85791F95696AB87D22E44F1BA30" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis_38879B2FA7E054DB8E8271C7830A050D" xlink:to="loc_us-gaap_ReceivableTypeDomain_5581C85791F95696AB87D22E44F1BA30" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LoansReceivableMember" xlink:label="loc_us-gaap_LoansReceivableMember_79F771EA5972522081A2E0A641A1B440" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ReceivableTypeDomain_5581C85791F95696AB87D22E44F1BA30" xlink:to="loc_us-gaap_LoansReceivableMember_79F771EA5972522081A2E0A641A1B440" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ValuationAllowancesAndReservesTypeAxis" xlink:label="loc_us-gaap_ValuationAllowancesAndReservesTypeAxis_11409303A2EB5EA8A7FFC02D4F2763A2" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFinancingReceivableAllowanceForCreditLossesTable_CFDFB9D79A5B551DA7723B41B0C385DA" xlink:to="loc_us-gaap_ValuationAllowancesAndReservesTypeAxis_11409303A2EB5EA8A7FFC02D4F2763A2" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ValuationAllowancesAndReservesDomain" xlink:label="loc_us-gaap_ValuationAllowancesAndReservesDomain_56B56DB1E07A7E70E870F786A6149B52_3639CE68F660501A8F4042849B1BEF0D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ValuationAllowancesAndReservesTypeAxis_11409303A2EB5EA8A7FFC02D4F2763A2" xlink:to="loc_us-gaap_ValuationAllowancesAndReservesDomain_56B56DB1E07A7E70E870F786A6149B52_3639CE68F660501A8F4042849B1BEF0D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ValuationAllowancesAndReservesDomain" xlink:label="loc_us-gaap_ValuationAllowancesAndReservesDomain_CF2EEFB6C2055F92814C1294B404A11C" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ValuationAllowancesAndReservesTypeAxis_11409303A2EB5EA8A7FFC02D4F2763A2" xlink:to="loc_us-gaap_ValuationAllowancesAndReservesDomain_CF2EEFB6C2055F92814C1294B404A11C" xlink:type="arc" />
    <link:loc xlink:href="ucbi-20190930.xsd#ucbi_AllowanceForUnfundedCommitmentMember" xlink:label="loc_ucbi_AllowanceForUnfundedCommitmentMember_A9B778E8A4FC5931AEF0CA7F795792AE" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ValuationAllowancesAndReservesDomain_CF2EEFB6C2055F92814C1294B404A11C" xlink:to="loc_ucbi_AllowanceForUnfundedCommitmentMember_A9B778E8A4FC5931AEF0CA7F795792AE" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FinancingReceivablePortfolioSegmentAxis" xlink:label="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_1E9BA69B05475E1585EBDB5DA4C2C73B" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFinancingReceivableAllowanceForCreditLossesTable_CFDFB9D79A5B551DA7723B41B0C385DA" xlink:to="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_1E9BA69B05475E1585EBDB5DA4C2C73B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FinancingReceivablePortfolioSegmentDomain" xlink:label="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_3F6F8F07B5C3A2606650F786A6162E2D_3639CE68F660501A8F4042849B1BEF0D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_1E9BA69B05475E1585EBDB5DA4C2C73B" xlink:to="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_3F6F8F07B5C3A2606650F786A6162E2D_3639CE68F660501A8F4042849B1BEF0D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FinancingReceivablePortfolioSegmentDomain" xlink:label="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_8A7871437D0B5ACA9AF4E7C7B9BF7765" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_1E9BA69B05475E1585EBDB5DA4C2C73B" xlink:to="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_8A7871437D0B5ACA9AF4E7C7B9BF7765" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CommercialPortfolioSegmentMember" xlink:label="loc_us-gaap_CommercialPortfolioSegmentMember_5B1C84D3F347529B9D419BA6001FDAA5" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_8A7871437D0B5ACA9AF4E7C7B9BF7765" xlink:to="loc_us-gaap_CommercialPortfolioSegmentMember_5B1C84D3F347529B9D419BA6001FDAA5" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ResidentialPortfolioSegmentMember" xlink:label="loc_us-gaap_ResidentialPortfolioSegmentMember_9D9791D80AEB59D49CF7BE1BDB8C3BF7" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_8A7871437D0B5ACA9AF4E7C7B9BF7765" xlink:to="loc_us-gaap_ResidentialPortfolioSegmentMember_9D9791D80AEB59D49CF7BE1BDB8C3BF7" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ConsumerPortfolioSegmentMember" xlink:label="loc_us-gaap_ConsumerPortfolioSegmentMember_DBA6D2FBFE47568E9E18B5589AD8E4BD" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_8A7871437D0B5ACA9AF4E7C7B9BF7765" xlink:to="loc_us-gaap_ConsumerPortfolioSegmentMember_DBA6D2FBFE47568E9E18B5589AD8E4BD" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_4F2DA801663B51C4AAA9281870A29706" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFinancingReceivableAllowanceForCreditLossesTable_CFDFB9D79A5B551DA7723B41B0C385DA" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_4F2DA801663B51C4AAA9281870A29706" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_EC323FCF2B60C968D487F786A616CB3C_3639CE68F660501A8F4042849B1BEF0D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_4F2DA801663B51C4AAA9281870A29706" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_EC323FCF2B60C968D487F786A616CB3C_3639CE68F660501A8F4042849B1BEF0D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_03534B3E4ACD50D3A2BA96905B9B39D0" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_4F2DA801663B51C4AAA9281870A29706" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_03534B3E4ACD50D3A2BA96905B9B39D0" xlink:type="arc" />
    <link:loc xlink:href="ucbi-20190930.xsd#ucbi_OwnerOccupiedCommercialRealEstateMember" xlink:label="loc_ucbi_OwnerOccupiedCommercialRealEstateMember_7D774D8098BF5660B8BDDBF1B9BCB55F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_03534B3E4ACD50D3A2BA96905B9B39D0" xlink:to="loc_ucbi_OwnerOccupiedCommercialRealEstateMember_7D774D8098BF5660B8BDDBF1B9BCB55F" xlink:type="arc" />
    <link:loc xlink:href="ucbi-20190930.xsd#ucbi_IncomeProducingCommercialRealEstateMember" xlink:label="loc_ucbi_IncomeProducingCommercialRealEstateMember_D34413D2E6EB5C1D8540409169164B1C" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_03534B3E4ACD50D3A2BA96905B9B39D0" xlink:to="loc_ucbi_IncomeProducingCommercialRealEstateMember_D34413D2E6EB5C1D8540409169164B1C" xlink:type="arc" />
    <link:loc xlink:href="ucbi-20190930.xsd#ucbi_CommercialAndIndustrialClassificationMember" xlink:label="loc_ucbi_CommercialAndIndustrialClassificationMember_E7E76633257059FAB9C40D0CE7D472CC" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_03534B3E4ACD50D3A2BA96905B9B39D0" xlink:to="loc_ucbi_CommercialAndIndustrialClassificationMember_E7E76633257059FAB9C40D0CE7D472CC" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ConstructionLoansMember" xlink:label="loc_us-gaap_ConstructionLoansMember_DB8B9A7970FA572EB03524F620284331" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_03534B3E4ACD50D3A2BA96905B9B39D0" xlink:to="loc_us-gaap_ConstructionLoansMember_DB8B9A7970FA572EB03524F620284331" xlink:type="arc" />
    <link:loc xlink:href="ucbi-20190930.xsd#ucbi_EquipmentFinancingMember" xlink:label="loc_ucbi_EquipmentFinancingMember_E1724A2878665158852FF722847CC190" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_03534B3E4ACD50D3A2BA96905B9B39D0" xlink:to="loc_ucbi_EquipmentFinancingMember_E1724A2878665158852FF722847CC190" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ResidentialMortgageMember" xlink:label="loc_us-gaap_ResidentialMortgageMember_905A86CC07355CDEBCA27B362C817BD8" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_03534B3E4ACD50D3A2BA96905B9B39D0" xlink:to="loc_us-gaap_ResidentialMortgageMember_905A86CC07355CDEBCA27B362C817BD8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_HomeEquityMember" xlink:label="loc_us-gaap_HomeEquityMember_2EA1A7AD36FA5D9A85B46E3727B4CA33" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_03534B3E4ACD50D3A2BA96905B9B39D0" xlink:to="loc_us-gaap_HomeEquityMember_2EA1A7AD36FA5D9A85B46E3727B4CA33" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AutomobileLoanMember" xlink:label="loc_us-gaap_AutomobileLoanMember_836512254D5A5037B514978E0F4AAE0C" xlink:type="locator" />
    <link:definitionArc order="8" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_03534B3E4ACD50D3A2BA96905B9B39D0" xlink:to="loc_us-gaap_AutomobileLoanMember_836512254D5A5037B514978E0F4AAE0C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FinancingReceivableAllowanceForCreditLossesRollForward" xlink:label="loc_us-gaap_FinancingReceivableAllowanceForCreditLossesRollForward_F7931F55CF98595FADFBB28F3FC9A965" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableAllowanceForCreditLossesLineItems_00704E9273FE54A8A260DCECC5B3D655" xlink:to="loc_us-gaap_FinancingReceivableAllowanceForCreditLossesRollForward_F7931F55CF98595FADFBB28F3FC9A965" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FinancingReceivableAllowanceForCreditLosses" xlink:label="loc_us-gaap_FinancingReceivableAllowanceForCreditLosses_00BAA7816F9552A6BEF030DC083F6940" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableAllowanceForCreditLossesRollForward_F7931F55CF98595FADFBB28F3FC9A965" xlink:to="loc_us-gaap_FinancingReceivableAllowanceForCreditLosses_00BAA7816F9552A6BEF030DC083F6940" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FinancingReceivableAllowanceForCreditLossesWriteOffs" xlink:label="loc_us-gaap_FinancingReceivableAllowanceForCreditLossesWriteOffs_EAF6ED5F46A85B1BB16FAD91B3F201F3" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableAllowanceForCreditLossesRollForward_F7931F55CF98595FADFBB28F3FC9A965" xlink:to="loc_us-gaap_FinancingReceivableAllowanceForCreditLossesWriteOffs_EAF6ED5F46A85B1BB16FAD91B3F201F3" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FinancingReceivableAllowanceForCreditLossesRecovery" xlink:label="loc_us-gaap_FinancingReceivableAllowanceForCreditLossesRecovery_6947026C26F95FB2BEFB8B035D4106CE" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableAllowanceForCreditLossesRollForward_F7931F55CF98595FADFBB28F3FC9A965" xlink:to="loc_us-gaap_FinancingReceivableAllowanceForCreditLossesRecovery_6947026C26F95FB2BEFB8B035D4106CE" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ProvisionForLoanAndLeaseLosses" xlink:label="loc_us-gaap_ProvisionForLoanAndLeaseLosses_22E44132F1815157935D02AF3CDC95A2" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableAllowanceForCreditLossesRollForward_F7931F55CF98595FADFBB28F3FC9A965" xlink:to="loc_us-gaap_ProvisionForLoanAndLeaseLosses_22E44132F1815157935D02AF3CDC95A2" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://ucbi.com/role/LoansAndLeasesAndAllowanceForCreditLossesChangesInValueOfAccretableYieldForAcquiredLoansDetails" xlink:type="extended" />
  <link:definitionLink xlink:role="http://ucbi.com/role/LoansAndLeasesAndAllowanceForCreditLossesComponentsOfNetInvestmentInLeasesDetails" xlink:type="extended" />
  <link:definitionLink xlink:role="http://ucbi.com/role/LoansAndLeasesAndAllowanceForCreditLossesLoansIndividuallyEvaluatedForImpairmentByClassOfLoansDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FinancingReceivableImpairedLineItems" xlink:label="loc_us-gaap_FinancingReceivableImpairedLineItems_AEE05592246A566385617D84A598E5E5" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ScheduleOfImpairedFinancingReceivableTable" xlink:label="loc_us-gaap_ScheduleOfImpairedFinancingReceivableTable_12AFC0ABFA815DFAA9CC07FB4980946B" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FinancingReceivableImpairedLineItems_AEE05592246A566385617D84A598E5E5" xlink:to="loc_us-gaap_ScheduleOfImpairedFinancingReceivableTable_12AFC0ABFA815DFAA9CC07FB4980946B" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis" xlink:label="loc_us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis_8E2455C053C15AF3AA4AEF61C9A3737C" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfImpairedFinancingReceivableTable_12AFC0ABFA815DFAA9CC07FB4980946B" xlink:to="loc_us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis_8E2455C053C15AF3AA4AEF61C9A3737C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ReceivableTypeDomain" xlink:label="loc_us-gaap_ReceivableTypeDomain_3D46BCD820855B9358BEF747E4F63864_3639CE68F660501A8F4042849B1BEF0D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis_8E2455C053C15AF3AA4AEF61C9A3737C" xlink:to="loc_us-gaap_ReceivableTypeDomain_3D46BCD820855B9358BEF747E4F63864_3639CE68F660501A8F4042849B1BEF0D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ReceivableTypeDomain" xlink:label="loc_us-gaap_ReceivableTypeDomain_D1024A72C85555C29F03FF598E9FC6E8" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis_8E2455C053C15AF3AA4AEF61C9A3737C" xlink:to="loc_us-gaap_ReceivableTypeDomain_D1024A72C85555C29F03FF598E9FC6E8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LoansReceivableMember" xlink:label="loc_us-gaap_LoansReceivableMember_3E65191378F4551AB0B4AC5DB10E50D3" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ReceivableTypeDomain_D1024A72C85555C29F03FF598E9FC6E8" xlink:to="loc_us-gaap_LoansReceivableMember_3E65191378F4551AB0B4AC5DB10E50D3" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FinancingReceivablePortfolioSegmentAxis" xlink:label="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_9F166CB50569509BACA5F406FE19C3D0" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfImpairedFinancingReceivableTable_12AFC0ABFA815DFAA9CC07FB4980946B" xlink:to="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_9F166CB50569509BACA5F406FE19C3D0" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FinancingReceivablePortfolioSegmentDomain" xlink:label="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_156E765A87A650240DDBF747E4F75A88_3639CE68F660501A8F4042849B1BEF0D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_9F166CB50569509BACA5F406FE19C3D0" xlink:to="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_156E765A87A650240DDBF747E4F75A88_3639CE68F660501A8F4042849B1BEF0D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FinancingReceivablePortfolioSegmentDomain" xlink:label="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_99A51BE48CDD52D19EE45449D550AE71" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_9F166CB50569509BACA5F406FE19C3D0" xlink:to="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_99A51BE48CDD52D19EE45449D550AE71" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CommercialPortfolioSegmentMember" xlink:label="loc_us-gaap_CommercialPortfolioSegmentMember_A522E52F1A8D5C5E8434C2234F9D4EFC" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_99A51BE48CDD52D19EE45449D550AE71" xlink:to="loc_us-gaap_CommercialPortfolioSegmentMember_A522E52F1A8D5C5E8434C2234F9D4EFC" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ResidentialPortfolioSegmentMember" xlink:label="loc_us-gaap_ResidentialPortfolioSegmentMember_5E8DD62A233452B4B0AFCAC3E5C7FFE7" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_99A51BE48CDD52D19EE45449D550AE71" xlink:to="loc_us-gaap_ResidentialPortfolioSegmentMember_5E8DD62A233452B4B0AFCAC3E5C7FFE7" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ConsumerPortfolioSegmentMember" xlink:label="loc_us-gaap_ConsumerPortfolioSegmentMember_76A6A24112F05A5F9AF474936E2918F0" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_99A51BE48CDD52D19EE45449D550AE71" xlink:to="loc_us-gaap_ConsumerPortfolioSegmentMember_76A6A24112F05A5F9AF474936E2918F0" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_D1055EBE8BEA503EA87FF80B6956E52C" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfImpairedFinancingReceivableTable_12AFC0ABFA815DFAA9CC07FB4980946B" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_D1055EBE8BEA503EA87FF80B6956E52C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_062A874AD543C01D299CF747E4F8E42E_3639CE68F660501A8F4042849B1BEF0D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_D1055EBE8BEA503EA87FF80B6956E52C" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_062A874AD543C01D299CF747E4F8E42E_3639CE68F660501A8F4042849B1BEF0D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_701131081EEE5BA88D0DD5A1CD14E42B" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_D1055EBE8BEA503EA87FF80B6956E52C" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_701131081EEE5BA88D0DD5A1CD14E42B" xlink:type="arc" />
    <link:loc xlink:href="ucbi-20190930.xsd#ucbi_OwnerOccupiedCommercialRealEstateMember" xlink:label="loc_ucbi_OwnerOccupiedCommercialRealEstateMember_E03D7EF251C25D38BC79342AD29C9559" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_701131081EEE5BA88D0DD5A1CD14E42B" xlink:to="loc_ucbi_OwnerOccupiedCommercialRealEstateMember_E03D7EF251C25D38BC79342AD29C9559" xlink:type="arc" />
    <link:loc xlink:href="ucbi-20190930.xsd#ucbi_IncomeProducingCommercialRealEstateMember" xlink:label="loc_ucbi_IncomeProducingCommercialRealEstateMember_BF457D50474059DEBFFA0876EF3CCEBD" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_701131081EEE5BA88D0DD5A1CD14E42B" xlink:to="loc_ucbi_IncomeProducingCommercialRealEstateMember_BF457D50474059DEBFFA0876EF3CCEBD" xlink:type="arc" />
    <link:loc xlink:href="ucbi-20190930.xsd#ucbi_CommercialAndIndustrialClassificationMember" xlink:label="loc_ucbi_CommercialAndIndustrialClassificationMember_C6FEBEE5C4CB59B18BFA3006A6ACD190" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_701131081EEE5BA88D0DD5A1CD14E42B" xlink:to="loc_ucbi_CommercialAndIndustrialClassificationMember_C6FEBEE5C4CB59B18BFA3006A6ACD190" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ConstructionLoansMember" xlink:label="loc_us-gaap_ConstructionLoansMember_D4CCD86DBDD55636AD7022E8DDBF1E65" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_701131081EEE5BA88D0DD5A1CD14E42B" xlink:to="loc_us-gaap_ConstructionLoansMember_D4CCD86DBDD55636AD7022E8DDBF1E65" xlink:type="arc" />
    <link:loc xlink:href="ucbi-20190930.xsd#ucbi_EquipmentFinancingMember" xlink:label="loc_ucbi_EquipmentFinancingMember_FE7FCF88DB1A5CC0AF15281CC480ECBC" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_701131081EEE5BA88D0DD5A1CD14E42B" xlink:to="loc_ucbi_EquipmentFinancingMember_FE7FCF88DB1A5CC0AF15281CC480ECBC" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ResidentialMortgageMember" xlink:label="loc_us-gaap_ResidentialMortgageMember_407297C9A1B0532E985E67F8ABDDA5EC" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_701131081EEE5BA88D0DD5A1CD14E42B" xlink:to="loc_us-gaap_ResidentialMortgageMember_407297C9A1B0532E985E67F8ABDDA5EC" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_HomeEquityMember" xlink:label="loc_us-gaap_HomeEquityMember_17D7655ED775565A9B38290C1D0F00BF" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_701131081EEE5BA88D0DD5A1CD14E42B" xlink:to="loc_us-gaap_HomeEquityMember_17D7655ED775565A9B38290C1D0F00BF" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AutomobileLoanMember" xlink:label="loc_us-gaap_AutomobileLoanMember_CFA7E6B6023B5AC49DDF631F3EF10E72" xlink:type="locator" />
    <link:definitionArc order="8" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_701131081EEE5BA88D0DD5A1CD14E42B" xlink:to="loc_us-gaap_AutomobileLoanMember_CFA7E6B6023B5AC49DDF631F3EF10E72" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FinancingReceivableRecordedInvestmentAgingAbstract" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentAgingAbstract_4DB0AB13C0FA52D5B180E5CB58F8B439" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableImpairedLineItems_AEE05592246A566385617D84A598E5E5" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentAgingAbstract_4DB0AB13C0FA52D5B180E5CB58F8B439" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ImpairedFinancingReceivableUnpaidPrincipalBalanceAbstract" xlink:label="loc_us-gaap_ImpairedFinancingReceivableUnpaidPrincipalBalanceAbstract_4317F465DCD45FCB8F2FC3390AA3F6BD" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentAgingAbstract_4DB0AB13C0FA52D5B180E5CB58F8B439" xlink:to="loc_us-gaap_ImpairedFinancingReceivableUnpaidPrincipalBalanceAbstract_4317F465DCD45FCB8F2FC3390AA3F6BD" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceUnpaidPrincipalBalance" xlink:label="loc_us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceUnpaidPrincipalBalance_B9ACCB8F3F4853FBA4227EA91C7B0260" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ImpairedFinancingReceivableUnpaidPrincipalBalanceAbstract_4317F465DCD45FCB8F2FC3390AA3F6BD" xlink:to="loc_us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceUnpaidPrincipalBalance_B9ACCB8F3F4853FBA4227EA91C7B0260" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceUnpaidPrincipalBalance" xlink:label="loc_us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceUnpaidPrincipalBalance_A556D6142C1E5DA79A7F067613EACAE7" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ImpairedFinancingReceivableUnpaidPrincipalBalanceAbstract_4317F465DCD45FCB8F2FC3390AA3F6BD" xlink:to="loc_us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceUnpaidPrincipalBalance_A556D6142C1E5DA79A7F067613EACAE7" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ImpairedFinancingReceivableUnpaidPrincipalBalance" xlink:label="loc_us-gaap_ImpairedFinancingReceivableUnpaidPrincipalBalance_04118A744FCC5949B64D02C0746F13AC" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ImpairedFinancingReceivableUnpaidPrincipalBalanceAbstract_4317F465DCD45FCB8F2FC3390AA3F6BD" xlink:to="loc_us-gaap_ImpairedFinancingReceivableUnpaidPrincipalBalance_04118A744FCC5949B64D02C0746F13AC" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ImpairedFinancingReceivableRecordedInvestmentAbstract" xlink:label="loc_us-gaap_ImpairedFinancingReceivableRecordedInvestmentAbstract_4FCDC4F8C3115603913E4EE453DF1193" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentAgingAbstract_4DB0AB13C0FA52D5B180E5CB58F8B439" xlink:to="loc_us-gaap_ImpairedFinancingReceivableRecordedInvestmentAbstract_4FCDC4F8C3115603913E4EE453DF1193" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceRecordedInvestment" xlink:label="loc_us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceRecordedInvestment_E7B84232DB7856118DABE9170EB90F0B" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ImpairedFinancingReceivableRecordedInvestmentAbstract_4FCDC4F8C3115603913E4EE453DF1193" xlink:to="loc_us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceRecordedInvestment_E7B84232DB7856118DABE9170EB90F0B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceRecordedInvestment" xlink:label="loc_us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceRecordedInvestment_96D4D3D1B0E65437958EC1BC760A4F2D" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ImpairedFinancingReceivableRecordedInvestmentAbstract_4FCDC4F8C3115603913E4EE453DF1193" xlink:to="loc_us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceRecordedInvestment_96D4D3D1B0E65437958EC1BC760A4F2D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ImpairedFinancingReceivableRecordedInvestment" xlink:label="loc_us-gaap_ImpairedFinancingReceivableRecordedInvestment_FB0C032CDD825B36A1B4CF0782DA2CD5" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ImpairedFinancingReceivableRecordedInvestmentAbstract_4FCDC4F8C3115603913E4EE453DF1193" xlink:to="loc_us-gaap_ImpairedFinancingReceivableRecordedInvestment_FB0C032CDD825B36A1B4CF0782DA2CD5" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ImpairedFinancingReceivableRelatedAllowance" xlink:label="loc_us-gaap_ImpairedFinancingReceivableRelatedAllowance_63BFFF9CCC3A52678CB35CC1FFB57BA4" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentAgingAbstract_4DB0AB13C0FA52D5B180E5CB58F8B439" xlink:to="loc_us-gaap_ImpairedFinancingReceivableRelatedAllowance_63BFFF9CCC3A52678CB35CC1FFB57BA4" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://ucbi.com/role/LoansAndLeasesAndAllowanceForCreditLossesLoansModifiedUnderTermsOfTdrDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FinancingReceivableModificationsLineItems" xlink:label="loc_us-gaap_FinancingReceivableModificationsLineItems_6F76BDBE0A4552D49C0FD54F6576A4AD" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ScheduleOfFinancingReceivableTroubledDebtRestructuringsTable" xlink:label="loc_us-gaap_ScheduleOfFinancingReceivableTroubledDebtRestructuringsTable_60705DD40F3B53C8A985D8142AF7565F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FinancingReceivableModificationsLineItems_6F76BDBE0A4552D49C0FD54F6576A4AD" xlink:to="loc_us-gaap_ScheduleOfFinancingReceivableTroubledDebtRestructuringsTable_60705DD40F3B53C8A985D8142AF7565F" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis" xlink:label="loc_us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis_B250C20135305D769B1E60936A64FC87" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFinancingReceivableTroubledDebtRestructuringsTable_60705DD40F3B53C8A985D8142AF7565F" xlink:to="loc_us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis_B250C20135305D769B1E60936A64FC87" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ReceivableTypeDomain" xlink:label="loc_us-gaap_ReceivableTypeDomain_81064A47FECCF40C72D9F8CC4B988F1C_3639CE68F660501A8F4042849B1BEF0D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis_B250C20135305D769B1E60936A64FC87" xlink:to="loc_us-gaap_ReceivableTypeDomain_81064A47FECCF40C72D9F8CC4B988F1C_3639CE68F660501A8F4042849B1BEF0D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ReceivableTypeDomain" xlink:label="loc_us-gaap_ReceivableTypeDomain_0AA03F2660CE509D80CFA47AFD8E5D90" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis_B250C20135305D769B1E60936A64FC87" xlink:to="loc_us-gaap_ReceivableTypeDomain_0AA03F2660CE509D80CFA47AFD8E5D90" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LoansReceivableMember" xlink:label="loc_us-gaap_LoansReceivableMember_C725E870934B520CB8CE03FEC4F00A0A" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ReceivableTypeDomain_0AA03F2660CE509D80CFA47AFD8E5D90" xlink:to="loc_us-gaap_LoansReceivableMember_C725E870934B520CB8CE03FEC4F00A0A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FinancingReceivablePortfolioSegmentAxis" xlink:label="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_EBB308E1A0415AC3A46326D2BD6E35F4" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFinancingReceivableTroubledDebtRestructuringsTable_60705DD40F3B53C8A985D8142AF7565F" xlink:to="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_EBB308E1A0415AC3A46326D2BD6E35F4" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FinancingReceivablePortfolioSegmentDomain" xlink:label="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_DED3878C0A6C0FC8025EF8CC4B99CFC6_3639CE68F660501A8F4042849B1BEF0D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_EBB308E1A0415AC3A46326D2BD6E35F4" xlink:to="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_DED3878C0A6C0FC8025EF8CC4B99CFC6_3639CE68F660501A8F4042849B1BEF0D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FinancingReceivablePortfolioSegmentDomain" xlink:label="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_B417257C62EB5FFEA2E29E39DC83556C" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_EBB308E1A0415AC3A46326D2BD6E35F4" xlink:to="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_B417257C62EB5FFEA2E29E39DC83556C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CommercialPortfolioSegmentMember" xlink:label="loc_us-gaap_CommercialPortfolioSegmentMember_725C4CC3C1B8533EA3233C65D1208856" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_B417257C62EB5FFEA2E29E39DC83556C" xlink:to="loc_us-gaap_CommercialPortfolioSegmentMember_725C4CC3C1B8533EA3233C65D1208856" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ResidentialPortfolioSegmentMember" xlink:label="loc_us-gaap_ResidentialPortfolioSegmentMember_0FE8F4A12B7C501B81216827261C7D91" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_B417257C62EB5FFEA2E29E39DC83556C" xlink:to="loc_us-gaap_ResidentialPortfolioSegmentMember_0FE8F4A12B7C501B81216827261C7D91" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ConsumerPortfolioSegmentMember" xlink:label="loc_us-gaap_ConsumerPortfolioSegmentMember_63D4FE71930F53ABB7EF9113A31C1F49" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_B417257C62EB5FFEA2E29E39DC83556C" xlink:to="loc_us-gaap_ConsumerPortfolioSegmentMember_63D4FE71930F53ABB7EF9113A31C1F49" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_140BAC52100D59E392D384C096C9C017" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFinancingReceivableTroubledDebtRestructuringsTable_60705DD40F3B53C8A985D8142AF7565F" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_140BAC52100D59E392D384C096C9C017" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_11E06139898A1BE30453F8CC4B9A9BDA_3639CE68F660501A8F4042849B1BEF0D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_140BAC52100D59E392D384C096C9C017" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_11E06139898A1BE30453F8CC4B9A9BDA_3639CE68F660501A8F4042849B1BEF0D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_8102ED7996A452FFB7C5E6086353D695" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_140BAC52100D59E392D384C096C9C017" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_8102ED7996A452FFB7C5E6086353D695" xlink:type="arc" />
    <link:loc xlink:href="ucbi-20190930.xsd#ucbi_OwnerOccupiedCommercialRealEstateMember" xlink:label="loc_ucbi_OwnerOccupiedCommercialRealEstateMember_2362BE2A31045A43B00F765B433C4150" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_8102ED7996A452FFB7C5E6086353D695" xlink:to="loc_ucbi_OwnerOccupiedCommercialRealEstateMember_2362BE2A31045A43B00F765B433C4150" xlink:type="arc" />
    <link:loc xlink:href="ucbi-20190930.xsd#ucbi_IncomeProducingCommercialRealEstateMember" xlink:label="loc_ucbi_IncomeProducingCommercialRealEstateMember_49962C429A7D5CCB975587FB18546CA2" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_8102ED7996A452FFB7C5E6086353D695" xlink:to="loc_ucbi_IncomeProducingCommercialRealEstateMember_49962C429A7D5CCB975587FB18546CA2" xlink:type="arc" />
    <link:loc xlink:href="ucbi-20190930.xsd#ucbi_CommercialAndIndustrialClassificationMember" xlink:label="loc_ucbi_CommercialAndIndustrialClassificationMember_78B7FD35165258458E48C546CA924683" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_8102ED7996A452FFB7C5E6086353D695" xlink:to="loc_ucbi_CommercialAndIndustrialClassificationMember_78B7FD35165258458E48C546CA924683" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ConstructionLoansMember" xlink:label="loc_us-gaap_ConstructionLoansMember_F780390A7BDB5F068DA16528A0B1DECC" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_8102ED7996A452FFB7C5E6086353D695" xlink:to="loc_us-gaap_ConstructionLoansMember_F780390A7BDB5F068DA16528A0B1DECC" xlink:type="arc" />
    <link:loc xlink:href="ucbi-20190930.xsd#ucbi_EquipmentFinancingMember" xlink:label="loc_ucbi_EquipmentFinancingMember_FA63D85781AE5B26911F5CCFE9F6BCFD" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_8102ED7996A452FFB7C5E6086353D695" xlink:to="loc_ucbi_EquipmentFinancingMember_FA63D85781AE5B26911F5CCFE9F6BCFD" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ResidentialMortgageMember" xlink:label="loc_us-gaap_ResidentialMortgageMember_D0CB07C7F4995BC4B658F576BD35845E" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_8102ED7996A452FFB7C5E6086353D695" xlink:to="loc_us-gaap_ResidentialMortgageMember_D0CB07C7F4995BC4B658F576BD35845E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_HomeEquityMember" xlink:label="loc_us-gaap_HomeEquityMember_77D47C0404445C609622A6E02BB4173E" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_8102ED7996A452FFB7C5E6086353D695" xlink:to="loc_us-gaap_HomeEquityMember_77D47C0404445C609622A6E02BB4173E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AutomobileLoanMember" xlink:label="loc_us-gaap_AutomobileLoanMember_25F251C719275C2CB58DEA8FE4EB71F3" xlink:type="locator" />
    <link:definitionArc order="8" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_8102ED7996A452FFB7C5E6086353D695" xlink:to="loc_us-gaap_AutomobileLoanMember_25F251C719275C2CB58DEA8FE4EB71F3" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LoanRestructuringModificationAxis" xlink:label="loc_us-gaap_LoanRestructuringModificationAxis_3782E99F799B5F1E86C57D3C6EF5C834" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFinancingReceivableTroubledDebtRestructuringsTable_60705DD40F3B53C8A985D8142AF7565F" xlink:to="loc_us-gaap_LoanRestructuringModificationAxis_3782E99F799B5F1E86C57D3C6EF5C834" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LoanRestructuringModificationDomain" xlink:label="loc_us-gaap_LoanRestructuringModificationDomain_530D330E6B9455753205F8CC4B9CF0FF_3639CE68F660501A8F4042849B1BEF0D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LoanRestructuringModificationAxis_3782E99F799B5F1E86C57D3C6EF5C834" xlink:to="loc_us-gaap_LoanRestructuringModificationDomain_530D330E6B9455753205F8CC4B9CF0FF_3639CE68F660501A8F4042849B1BEF0D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LoanRestructuringModificationDomain" xlink:label="loc_us-gaap_LoanRestructuringModificationDomain_32F1AC34A312571EA68F53D429987DB8" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LoanRestructuringModificationAxis_3782E99F799B5F1E86C57D3C6EF5C834" xlink:to="loc_us-gaap_LoanRestructuringModificationDomain_32F1AC34A312571EA68F53D429987DB8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ContractualInterestRateReductionMember" xlink:label="loc_us-gaap_ContractualInterestRateReductionMember_87F1833CBCE356799FFF8C361B849780" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LoanRestructuringModificationDomain_32F1AC34A312571EA68F53D429987DB8" xlink:to="loc_us-gaap_ContractualInterestRateReductionMember_87F1833CBCE356799FFF8C361B849780" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ExtendedMaturityMember" xlink:label="loc_us-gaap_ExtendedMaturityMember_687F2C28B63455CC8F9DBF1F6A738A09" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LoanRestructuringModificationDomain_32F1AC34A312571EA68F53D429987DB8" xlink:to="loc_us-gaap_ExtendedMaturityMember_687F2C28B63455CC8F9DBF1F6A738A09" xlink:type="arc" />
    <link:loc xlink:href="ucbi-20190930.xsd#ucbi_OtherTypeOfModificationMember" xlink:label="loc_ucbi_OtherTypeOfModificationMember_9F426D8D0D70522A88AF15763F133BBF" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LoanRestructuringModificationDomain_32F1AC34A312571EA68F53D429987DB8" xlink:to="loc_ucbi_OtherTypeOfModificationMember_9F426D8D0D70522A88AF15763F133BBF" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FinancingReceivableModificationsNumberOfContracts2" xlink:label="loc_us-gaap_FinancingReceivableModificationsNumberOfContracts2_39B7CD7AD196532CB0FC83B713099734" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableModificationsLineItems_6F76BDBE0A4552D49C0FD54F6576A4AD" xlink:to="loc_us-gaap_FinancingReceivableModificationsNumberOfContracts2_39B7CD7AD196532CB0FC83B713099734" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FinancingReceivableModificationsPreModificationRecordedInvestment2" xlink:label="loc_us-gaap_FinancingReceivableModificationsPreModificationRecordedInvestment2_F81FEF7F56BD5657AA44BDCD60C4DB7B" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableModificationsLineItems_6F76BDBE0A4552D49C0FD54F6576A4AD" xlink:to="loc_us-gaap_FinancingReceivableModificationsPreModificationRecordedInvestment2_F81FEF7F56BD5657AA44BDCD60C4DB7B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2" xlink:label="loc_us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2_1A9DC05984705560815E0A20B5CD4726" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableModificationsLineItems_6F76BDBE0A4552D49C0FD54F6576A4AD" xlink:to="loc_us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2_1A9DC05984705560815E0A20B5CD4726" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1" xlink:label="loc_us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1_2974643EC4805E2B9507AE3FD074DE0D" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableModificationsLineItems_6F76BDBE0A4552D49C0FD54F6576A4AD" xlink:to="loc_us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1_2974643EC4805E2B9507AE3FD074DE0D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1" xlink:label="loc_us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1_655D7115721B5628894AE32D7970DC90" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableModificationsLineItems_6F76BDBE0A4552D49C0FD54F6576A4AD" xlink:to="loc_us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1_655D7115721B5628894AE32D7970DC90" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://ucbi.com/role/LoansAndLeasesAndAllowanceForCreditLossesMajorClassificationsOfLoansDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LoansAndLeasesReceivableDisclosureLineItems" xlink:label="loc_us-gaap_LoansAndLeasesReceivableDisclosureLineItems_4AB8C3F3425E5584AC32F7F85422D3AC" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LoansAndLeasesReceivableDisclosureTable" xlink:label="loc_us-gaap_LoansAndLeasesReceivableDisclosureTable_481C230DAC645EDCB888EC2BCC95C569" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_LoansAndLeasesReceivableDisclosureLineItems_4AB8C3F3425E5584AC32F7F85422D3AC" xlink:to="loc_us-gaap_LoansAndLeasesReceivableDisclosureTable_481C230DAC645EDCB888EC2BCC95C569" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis" xlink:label="loc_us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis_CC9F49C7556355E892E81CAC896736D8" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LoansAndLeasesReceivableDisclosureTable_481C230DAC645EDCB888EC2BCC95C569" xlink:to="loc_us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis_CC9F49C7556355E892E81CAC896736D8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ReceivableTypeDomain" xlink:label="loc_us-gaap_ReceivableTypeDomain_B596518D1AC3504A9BC1F747E47E3F11_3639CE68F660501A8F4042849B1BEF0D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis_CC9F49C7556355E892E81CAC896736D8" xlink:to="loc_us-gaap_ReceivableTypeDomain_B596518D1AC3504A9BC1F747E47E3F11_3639CE68F660501A8F4042849B1BEF0D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ReceivableTypeDomain" xlink:label="loc_us-gaap_ReceivableTypeDomain_3BD27CC30B2B5CDB9C8130CA61D4BFD5" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis_CC9F49C7556355E892E81CAC896736D8" xlink:to="loc_us-gaap_ReceivableTypeDomain_3BD27CC30B2B5CDB9C8130CA61D4BFD5" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LoansReceivableMember" xlink:label="loc_us-gaap_LoansReceivableMember_6D7D12121308569DA26B35FA5059FE60" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ReceivableTypeDomain_3BD27CC30B2B5CDB9C8130CA61D4BFD5" xlink:to="loc_us-gaap_LoansReceivableMember_6D7D12121308569DA26B35FA5059FE60" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FinancingReceivablePortfolioSegmentAxis" xlink:label="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_F371100FC21C5650B6606B9C79BCCFDF" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LoansAndLeasesReceivableDisclosureTable_481C230DAC645EDCB888EC2BCC95C569" xlink:to="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_F371100FC21C5650B6606B9C79BCCFDF" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FinancingReceivablePortfolioSegmentDomain" xlink:label="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_D126D205FABE1F6C9B85F747E47EE19F_3639CE68F660501A8F4042849B1BEF0D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_F371100FC21C5650B6606B9C79BCCFDF" xlink:to="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_D126D205FABE1F6C9B85F747E47EE19F_3639CE68F660501A8F4042849B1BEF0D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FinancingReceivablePortfolioSegmentDomain" xlink:label="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_E5D49D6045075ADB91E7DCB2722EDCD6" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_F371100FC21C5650B6606B9C79BCCFDF" xlink:to="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_E5D49D6045075ADB91E7DCB2722EDCD6" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CommercialPortfolioSegmentMember" xlink:label="loc_us-gaap_CommercialPortfolioSegmentMember_61AD65AF6E295CEAB240445C47A2BCF4" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_E5D49D6045075ADB91E7DCB2722EDCD6" xlink:to="loc_us-gaap_CommercialPortfolioSegmentMember_61AD65AF6E295CEAB240445C47A2BCF4" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ResidentialPortfolioSegmentMember" xlink:label="loc_us-gaap_ResidentialPortfolioSegmentMember_97B4FD726C4A5026B108CA2ED7554134" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_E5D49D6045075ADB91E7DCB2722EDCD6" xlink:to="loc_us-gaap_ResidentialPortfolioSegmentMember_97B4FD726C4A5026B108CA2ED7554134" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ConsumerPortfolioSegmentMember" xlink:label="loc_us-gaap_ConsumerPortfolioSegmentMember_59468E9A6ADD5AC4AE5D9B1550B6EC98" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_E5D49D6045075ADB91E7DCB2722EDCD6" xlink:to="loc_us-gaap_ConsumerPortfolioSegmentMember_59468E9A6ADD5AC4AE5D9B1550B6EC98" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_70F4B9A5479F515C9C94E998467377BA" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LoansAndLeasesReceivableDisclosureTable_481C230DAC645EDCB888EC2BCC95C569" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_70F4B9A5479F515C9C94E998467377BA" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_4F328C82A3398408EC22F747E47FB6A2_3639CE68F660501A8F4042849B1BEF0D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_70F4B9A5479F515C9C94E998467377BA" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_4F328C82A3398408EC22F747E47FB6A2_3639CE68F660501A8F4042849B1BEF0D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_3A56E3057DB653A3A88DA9263161BE38" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_70F4B9A5479F515C9C94E998467377BA" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_3A56E3057DB653A3A88DA9263161BE38" xlink:type="arc" />
    <link:loc xlink:href="ucbi-20190930.xsd#ucbi_OwnerOccupiedCommercialRealEstateMember" xlink:label="loc_ucbi_OwnerOccupiedCommercialRealEstateMember_2222A59F537951CAA40C82CA1F02637B" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_3A56E3057DB653A3A88DA9263161BE38" xlink:to="loc_ucbi_OwnerOccupiedCommercialRealEstateMember_2222A59F537951CAA40C82CA1F02637B" xlink:type="arc" />
    <link:loc xlink:href="ucbi-20190930.xsd#ucbi_IncomeProducingCommercialRealEstateMember" xlink:label="loc_ucbi_IncomeProducingCommercialRealEstateMember_95AA7A6333B9554F8DEEA1B18E055933" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_3A56E3057DB653A3A88DA9263161BE38" xlink:to="loc_ucbi_IncomeProducingCommercialRealEstateMember_95AA7A6333B9554F8DEEA1B18E055933" xlink:type="arc" />
    <link:loc xlink:href="ucbi-20190930.xsd#ucbi_CommercialAndIndustrialClassificationMember" xlink:label="loc_ucbi_CommercialAndIndustrialClassificationMember_E03D5A397AAA56BB90EAAE2A9EA43599" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_3A56E3057DB653A3A88DA9263161BE38" xlink:to="loc_ucbi_CommercialAndIndustrialClassificationMember_E03D5A397AAA56BB90EAAE2A9EA43599" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ResidentialMortgageMember" xlink:label="loc_us-gaap_ResidentialMortgageMember_C84F140DA0685179A81DCEFC95042E28" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_3A56E3057DB653A3A88DA9263161BE38" xlink:to="loc_us-gaap_ResidentialMortgageMember_C84F140DA0685179A81DCEFC95042E28" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_HomeEquityMember" xlink:label="loc_us-gaap_HomeEquityMember_476ED6FBA97C5151813F4E371B32CEA3" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_3A56E3057DB653A3A88DA9263161BE38" xlink:to="loc_us-gaap_HomeEquityMember_476ED6FBA97C5151813F4E371B32CEA3" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ConstructionLoansMember" xlink:label="loc_us-gaap_ConstructionLoansMember_CD56FCC6A39D5499BF042BEB272CAA6B" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_3A56E3057DB653A3A88DA9263161BE38" xlink:to="loc_us-gaap_ConstructionLoansMember_CD56FCC6A39D5499BF042BEB272CAA6B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AutomobileLoanMember" xlink:label="loc_us-gaap_AutomobileLoanMember_C4FD4A1F074B5848B366C6D52F78CCA8" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_3A56E3057DB653A3A88DA9263161BE38" xlink:to="loc_us-gaap_AutomobileLoanMember_C4FD4A1F074B5848B366C6D52F78CCA8" xlink:type="arc" />
    <link:loc xlink:href="ucbi-20190930.xsd#ucbi_EquipmentFinancingMember" xlink:label="loc_ucbi_EquipmentFinancingMember_AAF5D54E70125D41A304E71AEB59678E" xlink:type="locator" />
    <link:definitionArc order="8" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_3A56E3057DB653A3A88DA9263161BE38" xlink:to="loc_ucbi_EquipmentFinancingMember_AAF5D54E70125D41A304E71AEB59678E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LoansAndLeasesReceivableNetReportedAmountAbstract" xlink:label="loc_us-gaap_LoansAndLeasesReceivableNetReportedAmountAbstract_EC98F80C19495A9F817F02AD91883695" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LoansAndLeasesReceivableDisclosureLineItems_4AB8C3F3425E5584AC32F7F85422D3AC" xlink:to="loc_us-gaap_LoansAndLeasesReceivableNetReportedAmountAbstract_EC98F80C19495A9F817F02AD91883695" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome" xlink:label="loc_us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome_395AFE0F0CD95523B39E4FA26189A115" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LoansAndLeasesReceivableNetReportedAmountAbstract_EC98F80C19495A9F817F02AD91883695" xlink:to="loc_us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome_395AFE0F0CD95523B39E4FA26189A115" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LoansAndLeasesReceivableAllowance" xlink:label="loc_us-gaap_LoansAndLeasesReceivableAllowance_82B73C5D2B805DC7BDA10797CB1189AF" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LoansAndLeasesReceivableNetReportedAmountAbstract_EC98F80C19495A9F817F02AD91883695" xlink:to="loc_us-gaap_LoansAndLeasesReceivableAllowance_82B73C5D2B805DC7BDA10797CB1189AF" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LoansAndLeasesReceivableNetReportedAmount" xlink:label="loc_us-gaap_LoansAndLeasesReceivableNetReportedAmount_0BABA15C2C8055DDA2FC34FA219B2195" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LoansAndLeasesReceivableNetReportedAmountAbstract_EC98F80C19495A9F817F02AD91883695" xlink:to="loc_us-gaap_LoansAndLeasesReceivableNetReportedAmount_0BABA15C2C8055DDA2FC34FA219B2195" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://ucbi.com/role/LoansAndLeasesAndAllowanceForCreditLossesMinimumFutureLeasePaymentToBeReceivedDetails" xlink:type="extended" />
  <link:definitionLink xlink:role="http://ucbi.com/role/LoansAndLeasesAndAllowanceForCreditLossesNarrativeDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AccountsNotesAndLoansReceivableLineItems" xlink:label="loc_us-gaap_AccountsNotesAndLoansReceivableLineItems_8056EFF6DD58A08D95FF42AB1237D85C" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ScheduleOfAccountsNotesLoansAndFinancingReceivableTable" xlink:label="loc_us-gaap_ScheduleOfAccountsNotesLoansAndFinancingReceivableTable_6D6AC61D30DA5CCE3FCB42AB1234F95A" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_AccountsNotesAndLoansReceivableLineItems_8056EFF6DD58A08D95FF42AB1237D85C" xlink:to="loc_us-gaap_ScheduleOfAccountsNotesLoansAndFinancingReceivableTable_6D6AC61D30DA5CCE3FCB42AB1234F95A" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_InvestmentTypeAxis" xlink:label="loc_us-gaap_InvestmentTypeAxis_64C15B61BFEB9DB8AE5842AB1234E19A" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfAccountsNotesLoansAndFinancingReceivableTable_6D6AC61D30DA5CCE3FCB42AB1234F95A" xlink:to="loc_us-gaap_InvestmentTypeAxis_64C15B61BFEB9DB8AE5842AB1234E19A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_InvestmentTypeCategorizationMember" xlink:label="loc_us-gaap_InvestmentTypeCategorizationMember_4966EC0FF9D6CB75031A42AB123514CB_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_InvestmentTypeAxis_64C15B61BFEB9DB8AE5842AB1234E19A" xlink:to="loc_us-gaap_InvestmentTypeCategorizationMember_4966EC0FF9D6CB75031A42AB123514CB_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_InvestmentTypeCategorizationMember" xlink:label="loc_us-gaap_InvestmentTypeCategorizationMember_4966EC0FF9D6CB75031A42AB123514CB" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_InvestmentTypeAxis_64C15B61BFEB9DB8AE5842AB1234E19A" xlink:to="loc_us-gaap_InvestmentTypeCategorizationMember_4966EC0FF9D6CB75031A42AB123514CB" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FederalHomeLoanBankCertificatesAndObligationsFHLBMember" xlink:label="loc_us-gaap_FederalHomeLoanBankCertificatesAndObligationsFHLBMember_B4EF88D50C637414D7B242AB1235D4E5" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InvestmentTypeCategorizationMember_4966EC0FF9D6CB75031A42AB123514CB" xlink:to="loc_us-gaap_FederalHomeLoanBankCertificatesAndObligationsFHLBMember_B4EF88D50C637414D7B242AB1235D4E5" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis" xlink:label="loc_us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis_1BE28544A729C585E11842AB1235023E" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfAccountsNotesLoansAndFinancingReceivableTable_6D6AC61D30DA5CCE3FCB42AB1234F95A" xlink:to="loc_us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis_1BE28544A729C585E11842AB1235023E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ReceivableTypeDomain" xlink:label="loc_us-gaap_ReceivableTypeDomain_7AC8BCC890559D77FD7842AB12358C18_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis_1BE28544A729C585E11842AB1235023E" xlink:to="loc_us-gaap_ReceivableTypeDomain_7AC8BCC890559D77FD7842AB12358C18_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ReceivableTypeDomain" xlink:label="loc_us-gaap_ReceivableTypeDomain_7AC8BCC890559D77FD7842AB12358C18" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis_1BE28544A729C585E11842AB1235023E" xlink:to="loc_us-gaap_ReceivableTypeDomain_7AC8BCC890559D77FD7842AB12358C18" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LoansReceivableMember" xlink:label="loc_us-gaap_LoansReceivableMember_83A163F1E327F262228F42AB1236CCA7" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ReceivableTypeDomain_7AC8BCC890559D77FD7842AB12358C18" xlink:to="loc_us-gaap_LoansReceivableMember_83A163F1E327F262228F42AB1236CCA7" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_34521420C774603913B442AB12369B86" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfAccountsNotesLoansAndFinancingReceivableTable_6D6AC61D30DA5CCE3FCB42AB1234F95A" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_34521420C774603913B442AB12369B86" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_C195C15F172448DCD2A642AB1236603E_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_34521420C774603913B442AB12369B86" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_C195C15F172448DCD2A642AB1236603E_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_C195C15F172448DCD2A642AB1236603E" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_34521420C774603913B442AB12369B86" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_C195C15F172448DCD2A642AB1236603E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AutomobileLoanMember" xlink:label="loc_us-gaap_AutomobileLoanMember_D42E712D2878D4DA12C442AB1236E268" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_C195C15F172448DCD2A642AB1236603E" xlink:to="loc_us-gaap_AutomobileLoanMember_D42E712D2878D4DA12C442AB1236E268" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LoansPledgedAsCollateral" xlink:label="loc_us-gaap_LoansPledgedAsCollateral_E6C8646373B6E7F70E3142AB123765F2" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccountsNotesAndLoansReceivableLineItems_8056EFF6DD58A08D95FF42AB1237D85C" xlink:to="loc_us-gaap_LoansPledgedAsCollateral_E6C8646373B6E7F70E3142AB123765F2" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CertainLoansAcquiredInTransferNotAccountedForAsDebtSecuritiesCarryingAmountNet" xlink:label="loc_us-gaap_CertainLoansAcquiredInTransferNotAccountedForAsDebtSecuritiesCarryingAmountNet_73D1FA8AE08C037B52A842AB12373F52" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccountsNotesAndLoansReceivableLineItems_8056EFF6DD58A08D95FF42AB1237D85C" xlink:to="loc_us-gaap_CertainLoansAcquiredInTransferNotAccountedForAsDebtSecuritiesCarryingAmountNet_73D1FA8AE08C037B52A842AB12373F52" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CertainLoansAcquiredInTransferNotAccountedForAsDebtSecuritiesOutstandingBalance" xlink:label="loc_us-gaap_CertainLoansAcquiredInTransferNotAccountedForAsDebtSecuritiesOutstandingBalance_9EF9E37E08515D33D1CF42AB1237A52A" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccountsNotesAndLoansReceivableLineItems_8056EFF6DD58A08D95FF42AB1237D85C" xlink:to="loc_us-gaap_CertainLoansAcquiredInTransferNotAccountedForAsDebtSecuritiesOutstandingBalance_9EF9E37E08515D33D1CF42AB1237A52A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_UnamortizedLoanCommitmentAndOriginationFeesAndUnamortizedDiscountsOrPremiums" xlink:label="loc_us-gaap_UnamortizedLoanCommitmentAndOriginationFeesAndUnamortizedDiscountsOrPremiums_48F03B08EDE4412729E942AB12373020" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccountsNotesAndLoansReceivableLineItems_8056EFF6DD58A08D95FF42AB1237D85C" xlink:to="loc_us-gaap_UnamortizedLoanCommitmentAndOriginationFeesAndUnamortizedDiscountsOrPremiums_48F03B08EDE4412729E942AB12373020" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_NetInvestmentInLease" xlink:label="loc_us-gaap_NetInvestmentInLease_1E19D9BEFD18434030D242AB12384FF7" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccountsNotesAndLoansReceivableLineItems_8056EFF6DD58A08D95FF42AB1237D85C" xlink:to="loc_us-gaap_NetInvestmentInLease_1E19D9BEFD18434030D242AB12384FF7" xlink:type="arc" />
    <link:loc xlink:href="ucbi-20190930.xsd#ucbi_MinimumAmountOfLoanEvaluatedForImpairment" xlink:label="loc_ucbi_MinimumAmountOfLoanEvaluatedForImpairment_B59AFC0295C42776E32B42AB1238AB27" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccountsNotesAndLoansReceivableLineItems_8056EFF6DD58A08D95FF42AB1237D85C" xlink:to="loc_ucbi_MinimumAmountOfLoanEvaluatedForImpairment_B59AFC0295C42776E32B42AB1238AB27" xlink:type="arc" />
    <link:loc xlink:href="ucbi-20190930.xsd#ucbi_SpecificReservesAllocatedToCustomersWhoseLoanTermsModifiedInTroubledDebtRestructurings" xlink:label="loc_ucbi_SpecificReservesAllocatedToCustomersWhoseLoanTermsModifiedInTroubledDebtRestructurings_F1CF6DC55E78EA39D3CF42AB123897A2" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccountsNotesAndLoansReceivableLineItems_8056EFF6DD58A08D95FF42AB1237D85C" xlink:to="loc_ucbi_SpecificReservesAllocatedToCustomersWhoseLoanTermsModifiedInTroubledDebtRestructurings_F1CF6DC55E78EA39D3CF42AB123897A2" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LoansAndLeasesReceivableImpairedCommitmentToLend" xlink:label="loc_us-gaap_LoansAndLeasesReceivableImpairedCommitmentToLend_0888E6A2969CC4A9097542AB12389347" xlink:type="locator" />
    <link:definitionArc order="8" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccountsNotesAndLoansReceivableLineItems_8056EFF6DD58A08D95FF42AB1237D85C" xlink:to="loc_us-gaap_LoansAndLeasesReceivableImpairedCommitmentToLend_0888E6A2969CC4A9097542AB12389347" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LoansAndLeasesReceivableImpairedInterestLostOnNonaccrualLoans" xlink:label="loc_us-gaap_LoansAndLeasesReceivableImpairedInterestLostOnNonaccrualLoans_FE02594A2661176289FB42AB1238AF0C" xlink:type="locator" />
    <link:definitionArc order="9" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccountsNotesAndLoansReceivableLineItems_8056EFF6DD58A08D95FF42AB1237D85C" xlink:to="loc_us-gaap_LoansAndLeasesReceivableImpairedInterestLostOnNonaccrualLoans_FE02594A2661176289FB42AB1238AF0C" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://ucbi.com/role/LoansAndLeasesAndAllowanceForCreditLossesRecordedInvestmentInLoansByPortfolioSegmentAndBalanceOfAllowanceForLoanLossesDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FinancingReceivableAllowanceForCreditLossesLineItems" xlink:label="loc_us-gaap_FinancingReceivableAllowanceForCreditLossesLineItems_83222F0EFECA50AA9845CB9681A4CF91" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ScheduleOfFinancingReceivableAllowanceForCreditLossesTable" xlink:label="loc_us-gaap_ScheduleOfFinancingReceivableAllowanceForCreditLossesTable_60588D181A805887B37592A79519BA6F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FinancingReceivableAllowanceForCreditLossesLineItems_83222F0EFECA50AA9845CB9681A4CF91" xlink:to="loc_us-gaap_ScheduleOfFinancingReceivableAllowanceForCreditLossesTable_60588D181A805887B37592A79519BA6F" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis" xlink:label="loc_us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis_19CA7D20CA495979A33AEC3DD58E5BE3" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFinancingReceivableAllowanceForCreditLossesTable_60588D181A805887B37592A79519BA6F" xlink:to="loc_us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis_19CA7D20CA495979A33AEC3DD58E5BE3" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ReceivableTypeDomain" xlink:label="loc_us-gaap_ReceivableTypeDomain_E43E18106A2AA9445B1AF747E0D6CB8D_3639CE68F660501A8F4042849B1BEF0D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis_19CA7D20CA495979A33AEC3DD58E5BE3" xlink:to="loc_us-gaap_ReceivableTypeDomain_E43E18106A2AA9445B1AF747E0D6CB8D_3639CE68F660501A8F4042849B1BEF0D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ReceivableTypeDomain" xlink:label="loc_us-gaap_ReceivableTypeDomain_A184AFA99976531C829005D5602F8C0E" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis_19CA7D20CA495979A33AEC3DD58E5BE3" xlink:to="loc_us-gaap_ReceivableTypeDomain_A184AFA99976531C829005D5602F8C0E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LoansReceivableMember" xlink:label="loc_us-gaap_LoansReceivableMember_0D1CF47B364C57F58CA107EBE44C1D5E" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ReceivableTypeDomain_A184AFA99976531C829005D5602F8C0E" xlink:to="loc_us-gaap_LoansReceivableMember_0D1CF47B364C57F58CA107EBE44C1D5E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ValuationAllowancesAndReservesTypeAxis" xlink:label="loc_us-gaap_ValuationAllowancesAndReservesTypeAxis_3C970F81DDA85868B06CCBD675202802" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFinancingReceivableAllowanceForCreditLossesTable_60588D181A805887B37592A79519BA6F" xlink:to="loc_us-gaap_ValuationAllowancesAndReservesTypeAxis_3C970F81DDA85868B06CCBD675202802" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ValuationAllowancesAndReservesDomain" xlink:label="loc_us-gaap_ValuationAllowancesAndReservesDomain_83413E49DF5687815AB7F747E0D7195D_3639CE68F660501A8F4042849B1BEF0D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ValuationAllowancesAndReservesTypeAxis_3C970F81DDA85868B06CCBD675202802" xlink:to="loc_us-gaap_ValuationAllowancesAndReservesDomain_83413E49DF5687815AB7F747E0D7195D_3639CE68F660501A8F4042849B1BEF0D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ValuationAllowancesAndReservesDomain" xlink:label="loc_us-gaap_ValuationAllowancesAndReservesDomain_247258DA4C0056B6A41129F705E94890" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ValuationAllowancesAndReservesTypeAxis_3C970F81DDA85868B06CCBD675202802" xlink:to="loc_us-gaap_ValuationAllowancesAndReservesDomain_247258DA4C0056B6A41129F705E94890" xlink:type="arc" />
    <link:loc xlink:href="ucbi-20190930.xsd#ucbi_AllowanceForUnfundedCommitmentMember" xlink:label="loc_ucbi_AllowanceForUnfundedCommitmentMember_3DBFBECB7BAE573D9E16D2F55E08DC0B" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ValuationAllowancesAndReservesDomain_247258DA4C0056B6A41129F705E94890" xlink:to="loc_ucbi_AllowanceForUnfundedCommitmentMember_3DBFBECB7BAE573D9E16D2F55E08DC0B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FinancingReceivablePortfolioSegmentAxis" xlink:label="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_49947894A02052A683F5FE363C652285" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFinancingReceivableAllowanceForCreditLossesTable_60588D181A805887B37592A79519BA6F" xlink:to="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_49947894A02052A683F5FE363C652285" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FinancingReceivablePortfolioSegmentDomain" xlink:label="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_F47372121995977D1EC3F747E0D79EF6_3639CE68F660501A8F4042849B1BEF0D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_49947894A02052A683F5FE363C652285" xlink:to="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_F47372121995977D1EC3F747E0D79EF6_3639CE68F660501A8F4042849B1BEF0D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FinancingReceivablePortfolioSegmentDomain" xlink:label="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_4624A94AA3AC501BBB4AE26F13B53225" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_49947894A02052A683F5FE363C652285" xlink:to="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_4624A94AA3AC501BBB4AE26F13B53225" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CommercialPortfolioSegmentMember" xlink:label="loc_us-gaap_CommercialPortfolioSegmentMember_9F83A130AAEB5B60976804E648DE1017" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_4624A94AA3AC501BBB4AE26F13B53225" xlink:to="loc_us-gaap_CommercialPortfolioSegmentMember_9F83A130AAEB5B60976804E648DE1017" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ResidentialPortfolioSegmentMember" xlink:label="loc_us-gaap_ResidentialPortfolioSegmentMember_21132C7BA69855C1B83629D924E7FB79" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_4624A94AA3AC501BBB4AE26F13B53225" xlink:to="loc_us-gaap_ResidentialPortfolioSegmentMember_21132C7BA69855C1B83629D924E7FB79" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ConsumerPortfolioSegmentMember" xlink:label="loc_us-gaap_ConsumerPortfolioSegmentMember_A944F5E301DA5C4B9EB135BB8ABAE25D" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_4624A94AA3AC501BBB4AE26F13B53225" xlink:to="loc_us-gaap_ConsumerPortfolioSegmentMember_A944F5E301DA5C4B9EB135BB8ABAE25D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_09D20D171032559292CC4F7B00C2CFA2" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFinancingReceivableAllowanceForCreditLossesTable_60588D181A805887B37592A79519BA6F" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_09D20D171032559292CC4F7B00C2CFA2" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_4840D3D9124201ACEC4BF747E0D91BC3_3639CE68F660501A8F4042849B1BEF0D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_09D20D171032559292CC4F7B00C2CFA2" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_4840D3D9124201ACEC4BF747E0D91BC3_3639CE68F660501A8F4042849B1BEF0D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_292848CED3BD5F0FA05367E009FD9E2F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_09D20D171032559292CC4F7B00C2CFA2" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_292848CED3BD5F0FA05367E009FD9E2F" xlink:type="arc" />
    <link:loc xlink:href="ucbi-20190930.xsd#ucbi_OwnerOccupiedCommercialRealEstateMember" xlink:label="loc_ucbi_OwnerOccupiedCommercialRealEstateMember_2EA1E9925DE85464B0E63FD55B302BC1" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_292848CED3BD5F0FA05367E009FD9E2F" xlink:to="loc_ucbi_OwnerOccupiedCommercialRealEstateMember_2EA1E9925DE85464B0E63FD55B302BC1" xlink:type="arc" />
    <link:loc xlink:href="ucbi-20190930.xsd#ucbi_IncomeProducingCommercialRealEstateMember" xlink:label="loc_ucbi_IncomeProducingCommercialRealEstateMember_5768AAF039D857CFB86475A2696038FF" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_292848CED3BD5F0FA05367E009FD9E2F" xlink:to="loc_ucbi_IncomeProducingCommercialRealEstateMember_5768AAF039D857CFB86475A2696038FF" xlink:type="arc" />
    <link:loc xlink:href="ucbi-20190930.xsd#ucbi_CommercialAndIndustrialClassificationMember" xlink:label="loc_ucbi_CommercialAndIndustrialClassificationMember_6A658427009A56E2A8CE62662837CC89" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_292848CED3BD5F0FA05367E009FD9E2F" xlink:to="loc_ucbi_CommercialAndIndustrialClassificationMember_6A658427009A56E2A8CE62662837CC89" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ConstructionLoansMember" xlink:label="loc_us-gaap_ConstructionLoansMember_856583EC507B5CAC92C9F4571FC79161" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_292848CED3BD5F0FA05367E009FD9E2F" xlink:to="loc_us-gaap_ConstructionLoansMember_856583EC507B5CAC92C9F4571FC79161" xlink:type="arc" />
    <link:loc xlink:href="ucbi-20190930.xsd#ucbi_EquipmentFinancingMember" xlink:label="loc_ucbi_EquipmentFinancingMember_9DE2C3F5DF165A74B5FDE484E0EC1D2B" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_292848CED3BD5F0FA05367E009FD9E2F" xlink:to="loc_ucbi_EquipmentFinancingMember_9DE2C3F5DF165A74B5FDE484E0EC1D2B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ResidentialMortgageMember" xlink:label="loc_us-gaap_ResidentialMortgageMember_DE59BB3F40C55FD0BEE969814A9C7DF2" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_292848CED3BD5F0FA05367E009FD9E2F" xlink:to="loc_us-gaap_ResidentialMortgageMember_DE59BB3F40C55FD0BEE969814A9C7DF2" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_HomeEquityMember" xlink:label="loc_us-gaap_HomeEquityMember_32B4CD38FD2C5F7DB06C6A18885BD3BA" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_292848CED3BD5F0FA05367E009FD9E2F" xlink:to="loc_us-gaap_HomeEquityMember_32B4CD38FD2C5F7DB06C6A18885BD3BA" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AutomobileLoanMember" xlink:label="loc_us-gaap_AutomobileLoanMember_275D5EEC3A855A9095F6E08E54E30DC7" xlink:type="locator" />
    <link:definitionArc order="8" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_292848CED3BD5F0FA05367E009FD9E2F" xlink:to="loc_us-gaap_AutomobileLoanMember_275D5EEC3A855A9095F6E08E54E30DC7" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1" xlink:label="loc_us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1_6C2113734AB359BCA4B498F35BB3521F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableAllowanceForCreditLossesLineItems_83222F0EFECA50AA9845CB9681A4CF91" xlink:to="loc_us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1_6C2113734AB359BCA4B498F35BB3521F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment" xlink:label="loc_us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment_3B4BE85FB5F35A33A42B5C395B782232" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableAllowanceForCreditLossesLineItems_83222F0EFECA50AA9845CB9681A4CF91" xlink:to="loc_us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment_3B4BE85FB5F35A33A42B5C395B782232" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CertainLoansAcquiredInTransferNotAccountedForAsDebtSecuritiesAllowanceForLoanLosses" xlink:label="loc_us-gaap_CertainLoansAcquiredInTransferNotAccountedForAsDebtSecuritiesAllowanceForLoanLosses_9EDFF9C42CA95485A362D64333AA5B80" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableAllowanceForCreditLossesLineItems_83222F0EFECA50AA9845CB9681A4CF91" xlink:to="loc_us-gaap_CertainLoansAcquiredInTransferNotAccountedForAsDebtSecuritiesAllowanceForLoanLosses_9EDFF9C42CA95485A362D64333AA5B80" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FinancingReceivableAllowanceForCreditLosses" xlink:label="loc_us-gaap_FinancingReceivableAllowanceForCreditLosses_BBA385E4DED15A70B1A4DE2708797FBC" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableAllowanceForCreditLossesLineItems_83222F0EFECA50AA9845CB9681A4CF91" xlink:to="loc_us-gaap_FinancingReceivableAllowanceForCreditLosses_BBA385E4DED15A70B1A4DE2708797FBC" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FinancingReceivableIndividuallyEvaluatedForImpairment" xlink:label="loc_us-gaap_FinancingReceivableIndividuallyEvaluatedForImpairment_F98AA4B5B27F5C5B82E98549AC9A8AE7" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableAllowanceForCreditLossesLineItems_83222F0EFECA50AA9845CB9681A4CF91" xlink:to="loc_us-gaap_FinancingReceivableIndividuallyEvaluatedForImpairment_F98AA4B5B27F5C5B82E98549AC9A8AE7" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment" xlink:label="loc_us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment_C357246FB7195C99B1213051F46E41F9" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableAllowanceForCreditLossesLineItems_83222F0EFECA50AA9845CB9681A4CF91" xlink:to="loc_us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment_C357246FB7195C99B1213051F46E41F9" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CertainLoansAcquiredInTransferNotAccountedForAsDebtSecuritiesCarryingAmountNet" xlink:label="loc_us-gaap_CertainLoansAcquiredInTransferNotAccountedForAsDebtSecuritiesCarryingAmountNet_6562D847C999520CB69C98C9DF57E110" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableAllowanceForCreditLossesLineItems_83222F0EFECA50AA9845CB9681A4CF91" xlink:to="loc_us-gaap_CertainLoansAcquiredInTransferNotAccountedForAsDebtSecuritiesCarryingAmountNet_6562D847C999520CB69C98C9DF57E110" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome" xlink:label="loc_us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome_94FEBCC39DFA5315B313D22659EE1C3C" xlink:type="locator" />
    <link:definitionArc order="8" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableAllowanceForCreditLossesLineItems_83222F0EFECA50AA9845CB9681A4CF91" xlink:to="loc_us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome_94FEBCC39DFA5315B313D22659EE1C3C" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://ucbi.com/role/LoansAndLeasesAndAllowanceForCreditLossesRecordedInvestmentInNonaccrualLoansByLoanClassDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FinancingReceivableRecordedInvestmentPastDueLineItems" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentPastDueLineItems_597CE7A0F2265DA5ACBB463283F786BC" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ScheduleOfFinancingReceivablesPastDueTable" xlink:label="loc_us-gaap_ScheduleOfFinancingReceivablesPastDueTable_38FBDD699F5A51CF86D7C3B7D6405A53" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentPastDueLineItems_597CE7A0F2265DA5ACBB463283F786BC" xlink:to="loc_us-gaap_ScheduleOfFinancingReceivablesPastDueTable_38FBDD699F5A51CF86D7C3B7D6405A53" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis" xlink:label="loc_us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis_63D914F73C5C5460A23968F6005A22A2" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFinancingReceivablesPastDueTable_38FBDD699F5A51CF86D7C3B7D6405A53" xlink:to="loc_us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis_63D914F73C5C5460A23968F6005A22A2" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ReceivableTypeDomain" xlink:label="loc_us-gaap_ReceivableTypeDomain_3CFFE5979F3FDC5ABA36F747E3038DC4_3639CE68F660501A8F4042849B1BEF0D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis_63D914F73C5C5460A23968F6005A22A2" xlink:to="loc_us-gaap_ReceivableTypeDomain_3CFFE5979F3FDC5ABA36F747E3038DC4_3639CE68F660501A8F4042849B1BEF0D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ReceivableTypeDomain" xlink:label="loc_us-gaap_ReceivableTypeDomain_FFFEF5998EEB5302867C600C1178EF06" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis_63D914F73C5C5460A23968F6005A22A2" xlink:to="loc_us-gaap_ReceivableTypeDomain_FFFEF5998EEB5302867C600C1178EF06" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LoansReceivableMember" xlink:label="loc_us-gaap_LoansReceivableMember_36C77CCA34A65A8A8132E9F49529AD76" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ReceivableTypeDomain_FFFEF5998EEB5302867C600C1178EF06" xlink:to="loc_us-gaap_LoansReceivableMember_36C77CCA34A65A8A8132E9F49529AD76" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FinancingReceivablePortfolioSegmentAxis" xlink:label="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_9182018D900D5EE882731632BD1DB277" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFinancingReceivablesPastDueTable_38FBDD699F5A51CF86D7C3B7D6405A53" xlink:to="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_9182018D900D5EE882731632BD1DB277" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FinancingReceivablePortfolioSegmentDomain" xlink:label="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_9483B1ABC5B122DEBBD7F747E304823F_3639CE68F660501A8F4042849B1BEF0D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_9182018D900D5EE882731632BD1DB277" xlink:to="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_9483B1ABC5B122DEBBD7F747E304823F_3639CE68F660501A8F4042849B1BEF0D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FinancingReceivablePortfolioSegmentDomain" xlink:label="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_CDDAEB8DCCFD5769AAFA951A8518B5A3" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_9182018D900D5EE882731632BD1DB277" xlink:to="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_CDDAEB8DCCFD5769AAFA951A8518B5A3" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CommercialPortfolioSegmentMember" xlink:label="loc_us-gaap_CommercialPortfolioSegmentMember_F0A0FD45C6B65D8D923EC727D1AA4A38" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_CDDAEB8DCCFD5769AAFA951A8518B5A3" xlink:to="loc_us-gaap_CommercialPortfolioSegmentMember_F0A0FD45C6B65D8D923EC727D1AA4A38" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ResidentialPortfolioSegmentMember" xlink:label="loc_us-gaap_ResidentialPortfolioSegmentMember_0E9C6C581B825CDE9B444687C1106FEE" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_CDDAEB8DCCFD5769AAFA951A8518B5A3" xlink:to="loc_us-gaap_ResidentialPortfolioSegmentMember_0E9C6C581B825CDE9B444687C1106FEE" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ConsumerPortfolioSegmentMember" xlink:label="loc_us-gaap_ConsumerPortfolioSegmentMember_3DC9962066AA54EF812BC06E559BBC31" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_CDDAEB8DCCFD5769AAFA951A8518B5A3" xlink:to="loc_us-gaap_ConsumerPortfolioSegmentMember_3DC9962066AA54EF812BC06E559BBC31" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_CA89978796615C42B3C6C527777C6C82" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFinancingReceivablesPastDueTable_38FBDD699F5A51CF86D7C3B7D6405A53" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_CA89978796615C42B3C6C527777C6C82" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_31BA6EA495F565CCFC6EF747E305F2E2_3639CE68F660501A8F4042849B1BEF0D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_CA89978796615C42B3C6C527777C6C82" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_31BA6EA495F565CCFC6EF747E305F2E2_3639CE68F660501A8F4042849B1BEF0D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_D067326AC927514599DB57C4CAF48038" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_CA89978796615C42B3C6C527777C6C82" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_D067326AC927514599DB57C4CAF48038" xlink:type="arc" />
    <link:loc xlink:href="ucbi-20190930.xsd#ucbi_OwnerOccupiedCommercialRealEstateMember" xlink:label="loc_ucbi_OwnerOccupiedCommercialRealEstateMember_7CB222B5E2735CD8B14A1D0FF6C5ECAE" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_D067326AC927514599DB57C4CAF48038" xlink:to="loc_ucbi_OwnerOccupiedCommercialRealEstateMember_7CB222B5E2735CD8B14A1D0FF6C5ECAE" xlink:type="arc" />
    <link:loc xlink:href="ucbi-20190930.xsd#ucbi_IncomeProducingCommercialRealEstateMember" xlink:label="loc_ucbi_IncomeProducingCommercialRealEstateMember_3738196F251B533DB4C90CAE28B6F623" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_D067326AC927514599DB57C4CAF48038" xlink:to="loc_ucbi_IncomeProducingCommercialRealEstateMember_3738196F251B533DB4C90CAE28B6F623" xlink:type="arc" />
    <link:loc xlink:href="ucbi-20190930.xsd#ucbi_CommercialAndIndustrialClassificationMember" xlink:label="loc_ucbi_CommercialAndIndustrialClassificationMember_D3083963144057429BE89FC440149E4B" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_D067326AC927514599DB57C4CAF48038" xlink:to="loc_ucbi_CommercialAndIndustrialClassificationMember_D3083963144057429BE89FC440149E4B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ResidentialMortgageMember" xlink:label="loc_us-gaap_ResidentialMortgageMember_7134912E54B5519F84B9125E1F1A9DFE" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_D067326AC927514599DB57C4CAF48038" xlink:to="loc_us-gaap_ResidentialMortgageMember_7134912E54B5519F84B9125E1F1A9DFE" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_HomeEquityMember" xlink:label="loc_us-gaap_HomeEquityMember_E45EAD3404AF5DE18C5BCD927BC605C5" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_D067326AC927514599DB57C4CAF48038" xlink:to="loc_us-gaap_HomeEquityMember_E45EAD3404AF5DE18C5BCD927BC605C5" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AutomobileLoanMember" xlink:label="loc_us-gaap_AutomobileLoanMember_D26693FA7452595FAC61EB4D5A0A2AE9" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_D067326AC927514599DB57C4CAF48038" xlink:to="loc_us-gaap_AutomobileLoanMember_D26693FA7452595FAC61EB4D5A0A2AE9" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ConstructionLoansMember" xlink:label="loc_us-gaap_ConstructionLoansMember_1A1853C24DB95263915B6DECEC8573BE" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_D067326AC927514599DB57C4CAF48038" xlink:to="loc_us-gaap_ConstructionLoansMember_1A1853C24DB95263915B6DECEC8573BE" xlink:type="arc" />
    <link:loc xlink:href="ucbi-20190930.xsd#ucbi_EquipmentFinancingMember" xlink:label="loc_ucbi_EquipmentFinancingMember_655BB74DFEC0511483BA1ADF9E3AF318" xlink:type="locator" />
    <link:definitionArc order="8" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_D067326AC927514599DB57C4CAF48038" xlink:to="loc_ucbi_EquipmentFinancingMember_655BB74DFEC0511483BA1ADF9E3AF318" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FinancingReceivableRecordedInvestmentAgingAbstract" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentAgingAbstract_63621F070F6754139E65116E7F527E07" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentPastDueLineItems_597CE7A0F2265DA5ACBB463283F786BC" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentAgingAbstract_63621F070F6754139E65116E7F527E07" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FinancingReceivableRecordedInvestmentNonaccrualStatus" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentNonaccrualStatus_34714E931AC9587A9B73685F4AA546A9" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentAgingAbstract_63621F070F6754139E65116E7F527E07" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentNonaccrualStatus_34714E931AC9587A9B73685F4AA546A9" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://ucbi.com/role/LoansAndLeasesAndAllowanceForCreditLossesRiskCategoryOfLoansByClassOfLoansDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FinancingReceivableRecordedInvestmentLineItems" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentLineItems_D1A2300299A7561AA99D17EF30FF5E0D" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ScheduleOfFinancingReceivableRecordedInvestmentCreditQualityIndicatorTable" xlink:label="loc_us-gaap_ScheduleOfFinancingReceivableRecordedInvestmentCreditQualityIndicatorTable_775D518A38E050DABC7C316C236A783C" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentLineItems_D1A2300299A7561AA99D17EF30FF5E0D" xlink:to="loc_us-gaap_ScheduleOfFinancingReceivableRecordedInvestmentCreditQualityIndicatorTable_775D518A38E050DABC7C316C236A783C" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis" xlink:label="loc_us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis_B687247F6B97589CA2B504D7538F2545" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFinancingReceivableRecordedInvestmentCreditQualityIndicatorTable_775D518A38E050DABC7C316C236A783C" xlink:to="loc_us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis_B687247F6B97589CA2B504D7538F2545" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ReceivableTypeDomain" xlink:label="loc_us-gaap_ReceivableTypeDomain_E8B7B724C255A29133D7F747E1979914_3639CE68F660501A8F4042849B1BEF0D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis_B687247F6B97589CA2B504D7538F2545" xlink:to="loc_us-gaap_ReceivableTypeDomain_E8B7B724C255A29133D7F747E1979914_3639CE68F660501A8F4042849B1BEF0D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ReceivableTypeDomain" xlink:label="loc_us-gaap_ReceivableTypeDomain_53F320326CA35763A2EA085641433BAD" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis_B687247F6B97589CA2B504D7538F2545" xlink:to="loc_us-gaap_ReceivableTypeDomain_53F320326CA35763A2EA085641433BAD" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LoansReceivableMember" xlink:label="loc_us-gaap_LoansReceivableMember_81A02AF4991B5D2BB00B703DA9CCB364" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ReceivableTypeDomain_53F320326CA35763A2EA085641433BAD" xlink:to="loc_us-gaap_LoansReceivableMember_81A02AF4991B5D2BB00B703DA9CCB364" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FinancingReceivablePortfolioSegmentAxis" xlink:label="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_6E24F5FDF9E35B14B14FBC6395687F44" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFinancingReceivableRecordedInvestmentCreditQualityIndicatorTable_775D518A38E050DABC7C316C236A783C" xlink:to="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_6E24F5FDF9E35B14B14FBC6395687F44" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FinancingReceivablePortfolioSegmentDomain" xlink:label="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_3C4FDC1628C225C3F290F747E1972EE5_3639CE68F660501A8F4042849B1BEF0D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_6E24F5FDF9E35B14B14FBC6395687F44" xlink:to="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_3C4FDC1628C225C3F290F747E1972EE5_3639CE68F660501A8F4042849B1BEF0D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FinancingReceivablePortfolioSegmentDomain" xlink:label="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_73E6317B1A7353CD94432B605D448AE2" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_6E24F5FDF9E35B14B14FBC6395687F44" xlink:to="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_73E6317B1A7353CD94432B605D448AE2" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CommercialPortfolioSegmentMember" xlink:label="loc_us-gaap_CommercialPortfolioSegmentMember_E14817E5A1EC5F97A86FD0C5DCF3492E" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_73E6317B1A7353CD94432B605D448AE2" xlink:to="loc_us-gaap_CommercialPortfolioSegmentMember_E14817E5A1EC5F97A86FD0C5DCF3492E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ResidentialPortfolioSegmentMember" xlink:label="loc_us-gaap_ResidentialPortfolioSegmentMember_123F469F5810544C85E848E7371B6FFA" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_73E6317B1A7353CD94432B605D448AE2" xlink:to="loc_us-gaap_ResidentialPortfolioSegmentMember_123F469F5810544C85E848E7371B6FFA" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ConsumerPortfolioSegmentMember" xlink:label="loc_us-gaap_ConsumerPortfolioSegmentMember_377781C7417C5D64BC97E27058FC152F" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_73E6317B1A7353CD94432B605D448AE2" xlink:to="loc_us-gaap_ConsumerPortfolioSegmentMember_377781C7417C5D64BC97E27058FC152F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_7B0770BC820D5D2CA4E7C8B922F7985C" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFinancingReceivableRecordedInvestmentCreditQualityIndicatorTable_775D518A38E050DABC7C316C236A783C" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_7B0770BC820D5D2CA4E7C8B922F7985C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_5CC41173875E9D82C481F747E1983227_3639CE68F660501A8F4042849B1BEF0D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_7B0770BC820D5D2CA4E7C8B922F7985C" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_5CC41173875E9D82C481F747E1983227_3639CE68F660501A8F4042849B1BEF0D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_20C3539186425A26A10CD4540DA27E27" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_7B0770BC820D5D2CA4E7C8B922F7985C" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_20C3539186425A26A10CD4540DA27E27" xlink:type="arc" />
    <link:loc xlink:href="ucbi-20190930.xsd#ucbi_OwnerOccupiedCommercialRealEstateMember" xlink:label="loc_ucbi_OwnerOccupiedCommercialRealEstateMember_CB8F9D12DDFF536886046A34F484178F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_20C3539186425A26A10CD4540DA27E27" xlink:to="loc_ucbi_OwnerOccupiedCommercialRealEstateMember_CB8F9D12DDFF536886046A34F484178F" xlink:type="arc" />
    <link:loc xlink:href="ucbi-20190930.xsd#ucbi_IncomeProducingCommercialRealEstateMember" xlink:label="loc_ucbi_IncomeProducingCommercialRealEstateMember_EE9D61A4C2CC56548850AE0B77F4BA87" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_20C3539186425A26A10CD4540DA27E27" xlink:to="loc_ucbi_IncomeProducingCommercialRealEstateMember_EE9D61A4C2CC56548850AE0B77F4BA87" xlink:type="arc" />
    <link:loc xlink:href="ucbi-20190930.xsd#ucbi_CommercialAndIndustrialClassificationMember" xlink:label="loc_ucbi_CommercialAndIndustrialClassificationMember_DF8BC9AAFCCB562AA0155C1DAAB84937" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_20C3539186425A26A10CD4540DA27E27" xlink:to="loc_ucbi_CommercialAndIndustrialClassificationMember_DF8BC9AAFCCB562AA0155C1DAAB84937" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ConstructionLoansMember" xlink:label="loc_us-gaap_ConstructionLoansMember_7050844E46CE56D5A656FAEDE7EE350E" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_20C3539186425A26A10CD4540DA27E27" xlink:to="loc_us-gaap_ConstructionLoansMember_7050844E46CE56D5A656FAEDE7EE350E" xlink:type="arc" />
    <link:loc xlink:href="ucbi-20190930.xsd#ucbi_EquipmentFinancingMember" xlink:label="loc_ucbi_EquipmentFinancingMember_BDFA86D424435C30B7D7A20FFB7A33C3" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_20C3539186425A26A10CD4540DA27E27" xlink:to="loc_ucbi_EquipmentFinancingMember_BDFA86D424435C30B7D7A20FFB7A33C3" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ResidentialMortgageMember" xlink:label="loc_us-gaap_ResidentialMortgageMember_BB36A215260457B7A675F7CD18534FFD" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_20C3539186425A26A10CD4540DA27E27" xlink:to="loc_us-gaap_ResidentialMortgageMember_BB36A215260457B7A675F7CD18534FFD" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_HomeEquityMember" xlink:label="loc_us-gaap_HomeEquityMember_51DB7EEABAF45246AAC5F27663EE7EA9" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_20C3539186425A26A10CD4540DA27E27" xlink:to="loc_us-gaap_HomeEquityMember_51DB7EEABAF45246AAC5F27663EE7EA9" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AutomobileLoanMember" xlink:label="loc_us-gaap_AutomobileLoanMember_DDD1F625AC66555BA5D6DF9772AFE30A" xlink:type="locator" />
    <link:definitionArc order="8" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_20C3539186425A26A10CD4540DA27E27" xlink:to="loc_us-gaap_AutomobileLoanMember_DDD1F625AC66555BA5D6DF9772AFE30A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_InternalCreditAssessmentAxis" xlink:label="loc_us-gaap_InternalCreditAssessmentAxis_0358C666D66059F5808B62A5F8727D6C" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFinancingReceivableRecordedInvestmentCreditQualityIndicatorTable_775D518A38E050DABC7C316C236A783C" xlink:to="loc_us-gaap_InternalCreditAssessmentAxis_0358C666D66059F5808B62A5F8727D6C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_InternalCreditAssessmentDomain" xlink:label="loc_us-gaap_InternalCreditAssessmentDomain_2BF016F8539D5269565BF747E19BAC1D_3639CE68F660501A8F4042849B1BEF0D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_InternalCreditAssessmentAxis_0358C666D66059F5808B62A5F8727D6C" xlink:to="loc_us-gaap_InternalCreditAssessmentDomain_2BF016F8539D5269565BF747E19BAC1D_3639CE68F660501A8F4042849B1BEF0D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_InternalCreditAssessmentDomain" xlink:label="loc_us-gaap_InternalCreditAssessmentDomain_2C6E2FC0AF43518C8E18D6C53A401DE1" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_InternalCreditAssessmentAxis_0358C666D66059F5808B62A5F8727D6C" xlink:to="loc_us-gaap_InternalCreditAssessmentDomain_2C6E2FC0AF43518C8E18D6C53A401DE1" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PassMember" xlink:label="loc_us-gaap_PassMember_77FCA0E32BBC5FE8A71FC40DB8FF392C" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InternalCreditAssessmentDomain_2C6E2FC0AF43518C8E18D6C53A401DE1" xlink:to="loc_us-gaap_PassMember_77FCA0E32BBC5FE8A71FC40DB8FF392C" xlink:type="arc" />
    <link:loc xlink:href="ucbi-20190930.xsd#ucbi_WatchMember" xlink:label="loc_ucbi_WatchMember_55BBFA72FF5D5B26998980225E2F537A" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InternalCreditAssessmentDomain_2C6E2FC0AF43518C8E18D6C53A401DE1" xlink:to="loc_ucbi_WatchMember_55BBFA72FF5D5B26998980225E2F537A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SubstandardMember" xlink:label="loc_us-gaap_SubstandardMember_E16E2DDA419250AD90E965489D8450CF" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InternalCreditAssessmentDomain_2C6E2FC0AF43518C8E18D6C53A401DE1" xlink:to="loc_us-gaap_SubstandardMember_E16E2DDA419250AD90E965489D8450CF" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DoubtfulMember" xlink:label="loc_us-gaap_DoubtfulMember_64DFE33925C9552CAC0DF6080C55D229" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InternalCreditAssessmentDomain_2C6E2FC0AF43518C8E18D6C53A401DE1" xlink:to="loc_us-gaap_DoubtfulMember_64DFE33925C9552CAC0DF6080C55D229" xlink:type="arc" />
    <link:loc xlink:href="ucbi-20190930.xsd#ucbi_RiskCategoryOfLoansByClassOfLoansAbstract" xlink:label="loc_ucbi_RiskCategoryOfLoansByClassOfLoansAbstract_73C40A521F885457800644183DF2127C" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentLineItems_D1A2300299A7561AA99D17EF30FF5E0D" xlink:to="loc_ucbi_RiskCategoryOfLoansByClassOfLoansAbstract_73C40A521F885457800644183DF2127C" xlink:type="arc" />
    <link:loc xlink:href="ucbi-20190930.xsd#ucbi_LoansAndLeasesReceivableExcludingPurchasedCreditImpairedLoans" xlink:label="loc_ucbi_LoansAndLeasesReceivableExcludingPurchasedCreditImpairedLoans_D0AFC7ED584A5784A8FCF07744BB5CBE" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ucbi_RiskCategoryOfLoansByClassOfLoansAbstract_73C40A521F885457800644183DF2127C" xlink:to="loc_ucbi_LoansAndLeasesReceivableExcludingPurchasedCreditImpairedLoans_D0AFC7ED584A5784A8FCF07744BB5CBE" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CertainLoansAcquiredInTransferNotAccountedForAsDebtSecuritiesCarryingAmountNet" xlink:label="loc_us-gaap_CertainLoansAcquiredInTransferNotAccountedForAsDebtSecuritiesCarryingAmountNet_3D961C73CB525056AB55188FC4050998" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ucbi_RiskCategoryOfLoansByClassOfLoansAbstract_73C40A521F885457800644183DF2127C" xlink:to="loc_us-gaap_CertainLoansAcquiredInTransferNotAccountedForAsDebtSecuritiesCarryingAmountNet_3D961C73CB525056AB55188FC4050998" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome" xlink:label="loc_us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome_87889C8B77FE58778EA0030015C583CE" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ucbi_RiskCategoryOfLoansByClassOfLoansAbstract_73C40A521F885457800644183DF2127C" xlink:to="loc_us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome_87889C8B77FE58778EA0030015C583CE" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://ucbi.com/role/LoansAndLeasesAndAllowanceForCreditLossesTables" xlink:type="extended" />
  <link:definitionLink xlink:role="http://ucbi.com/role/OperatingLeases" xlink:type="extended" />
  <link:definitionLink xlink:role="http://ucbi.com/role/OperatingLeasesFutureMinimumLeasePaymentsDetails" xlink:type="extended" />
  <link:definitionLink xlink:role="http://ucbi.com/role/OperatingLeasesNarrativeDetails" xlink:type="extended" />
  <link:definitionLink xlink:role="http://ucbi.com/role/OperatingLeasesOperatingLeaseIncomeAndExpenseAndOtherSupplementalInformationDetails" xlink:type="extended" />
  <link:definitionLink xlink:role="http://ucbi.com/role/OperatingLeasesTables" xlink:type="extended" />
  <link:definitionLink xlink:role="http://ucbi.com/role/ReclassificationsOutOfAccumulatedOtherComprehensiveIncome" xlink:type="extended" />
  <link:definitionLink xlink:role="http://ucbi.com/role/ReclassificationsOutOfAccumulatedOtherComprehensiveIncomeDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ReclassificationAdjustmentOutOfAccumulatedOtherComprehensiveIncomeLineItems" xlink:label="loc_us-gaap_ReclassificationAdjustmentOutOfAccumulatedOtherComprehensiveIncomeLineItems_A8F60B6557690359AA1742AB11B45B1B" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeTable" xlink:label="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeTable_ED2B63C54804D8B6983F42AB11B1C98C" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ReclassificationAdjustmentOutOfAccumulatedOtherComprehensiveIncomeLineItems_A8F60B6557690359AA1742AB11B45B1B" xlink:to="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeTable_ED2B63C54804D8B6983F42AB11B1C98C" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis" xlink:label="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis_6AD57F54F24CB792BFA942AB11B282D7" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeTable_ED2B63C54804D8B6983F42AB11B1C98C" xlink:to="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis_6AD57F54F24CB792BFA942AB11B282D7" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeDomain" xlink:label="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeDomain_5D2C739DA965E773A5CB42AB11B261B2_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis_6AD57F54F24CB792BFA942AB11B282D7" xlink:to="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeDomain_5D2C739DA965E773A5CB42AB11B261B2_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeDomain" xlink:label="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeDomain_5D2C739DA965E773A5CB42AB11B261B2" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis_6AD57F54F24CB792BFA942AB11B282D7" xlink:to="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeDomain_5D2C739DA965E773A5CB42AB11B261B2" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeMember" xlink:label="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeMember_5248909978406FA6ADCF42AB11B23ABA" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeDomain_5D2C739DA965E773A5CB42AB11B261B2" xlink:to="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeMember_5248909978406FA6ADCF42AB11B23ABA" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StatementEquityComponentsAxis" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_2CF92873EEC5B236A09042AB11B2F478" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeTable_ED2B63C54804D8B6983F42AB11B1C98C" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_2CF92873EEC5B236A09042AB11B2F478" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_EquityComponentDomain" xlink:label="loc_us-gaap_EquityComponentDomain_B8BCAD6A33DAB53B7AA642AB11B31EDF_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_2CF92873EEC5B236A09042AB11B2F478" xlink:to="loc_us-gaap_EquityComponentDomain_B8BCAD6A33DAB53B7AA642AB11B31EDF_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_EquityComponentDomain" xlink:label="loc_us-gaap_EquityComponentDomain_B8BCAD6A33DAB53B7AA642AB11B31EDF" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_2CF92873EEC5B236A09042AB11B2F478" xlink:to="loc_us-gaap_EquityComponentDomain_B8BCAD6A33DAB53B7AA642AB11B31EDF" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AccumulatedNetUnrealizedInvestmentGainLossMember" xlink:label="loc_us-gaap_AccumulatedNetUnrealizedInvestmentGainLossMember_D7646D103B1E4E01078842AB11B3E6A4" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_B8BCAD6A33DAB53B7AA642AB11B31EDF" xlink:to="loc_us-gaap_AccumulatedNetUnrealizedInvestmentGainLossMember_D7646D103B1E4E01078842AB11B3E6A4" xlink:type="arc" />
    <link:loc xlink:href="ucbi-20190930.xsd#ucbi_AccumulatedAmortizationOfGainsIncludedInNetIncomeOnAvailableForSaleSecuritiesTransferredToHeldToMaturityMember" xlink:label="loc_ucbi_AccumulatedAmortizationOfGainsIncludedInNetIncomeOnAvailableForSaleSecuritiesTransferredToHeldToMaturityMember_2FA463F790D0AB373EE942AB11B3261D" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_B8BCAD6A33DAB53B7AA642AB11B31EDF" xlink:to="loc_ucbi_AccumulatedAmortizationOfGainsIncludedInNetIncomeOnAvailableForSaleSecuritiesTransferredToHeldToMaturityMember_2FA463F790D0AB373EE942AB11B3261D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AccumulatedNetGainLossFromDesignatedOrQualifyingCashFlowHedgesMember" xlink:label="loc_us-gaap_AccumulatedNetGainLossFromDesignatedOrQualifyingCashFlowHedgesMember_80E5EE0B4838B4B1E76442AB11B3BEDF" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_B8BCAD6A33DAB53B7AA642AB11B31EDF" xlink:to="loc_us-gaap_AccumulatedNetGainLossFromDesignatedOrQualifyingCashFlowHedgesMember_80E5EE0B4838B4B1E76442AB11B3BEDF" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AccumulatedDefinedBenefitPlansAdjustmentNetPriorServiceCostCreditMember" xlink:label="loc_us-gaap_AccumulatedDefinedBenefitPlansAdjustmentNetPriorServiceCostCreditMember_85BF9BA44FA5D6D9EFA342AB11B3BC6B" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_B8BCAD6A33DAB53B7AA642AB11B31EDF" xlink:to="loc_us-gaap_AccumulatedDefinedBenefitPlansAdjustmentNetPriorServiceCostCreditMember_85BF9BA44FA5D6D9EFA342AB11B3BC6B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AccumulatedDefinedBenefitPlansAdjustmentNetUnamortizedGainLossMember" xlink:label="loc_us-gaap_AccumulatedDefinedBenefitPlansAdjustmentNetUnamortizedGainLossMember_033C7FC31D489536423742AB11B43530" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_B8BCAD6A33DAB53B7AA642AB11B31EDF" xlink:to="loc_us-gaap_AccumulatedDefinedBenefitPlansAdjustmentNetUnamortizedGainLossMember_033C7FC31D489536423742AB11B43530" xlink:type="arc" />
    <link:loc xlink:href="ucbi-20190930.xsd#ucbi_AccumulatedDefinedBenefitPlansAdjustmentNetLossOnPlanTerminationMember" xlink:label="loc_ucbi_AccumulatedDefinedBenefitPlansAdjustmentNetLossOnPlanTerminationMember_D8AE8874CF60DD57BD3E42AB11B43FF0" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_B8BCAD6A33DAB53B7AA642AB11B31EDF" xlink:to="loc_ucbi_AccumulatedDefinedBenefitPlansAdjustmentNetLossOnPlanTerminationMember_D8AE8874CF60DD57BD3E42AB11B43FF0" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember" xlink:label="loc_us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember_FE49E068A556B1BC880442AB11B4BE66" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_B8BCAD6A33DAB53B7AA642AB11B31EDF" xlink:to="loc_us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember_FE49E068A556B1BC880442AB11B4BE66" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtSecuritiesAvailableForSaleRealizedGainLoss" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleRealizedGainLoss_A335911ACA7363FE593042AB11B414BA" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ReclassificationAdjustmentOutOfAccumulatedOtherComprehensiveIncomeLineItems_A8F60B6557690359AA1742AB11B45B1B" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleRealizedGainLoss_A335911ACA7363FE593042AB11B414BA" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_InterestIncomeOperating" xlink:label="loc_us-gaap_InterestIncomeOperating_94E094FB277DF217EEC942AB11B5EBDF" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ReclassificationAdjustmentOutOfAccumulatedOtherComprehensiveIncomeLineItems_A8F60B6557690359AA1742AB11B45B1B" xlink:to="loc_us-gaap_InterestIncomeOperating_94E094FB277DF217EEC942AB11B5EBDF" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_InterestExpenseMoneyMarketDeposits" xlink:label="loc_us-gaap_InterestExpenseMoneyMarketDeposits_1790C10D3CDF345A091342AB11B55D85" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ReclassificationAdjustmentOutOfAccumulatedOtherComprehensiveIncomeLineItems_A8F60B6557690359AA1742AB11B45B1B" xlink:to="loc_us-gaap_InterestExpenseMoneyMarketDeposits_1790C10D3CDF345A091342AB11B55D85" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LaborAndRelatedExpense" xlink:label="loc_us-gaap_LaborAndRelatedExpense_7A84D9207EB08AF3365742AB11B5243E" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ReclassificationAdjustmentOutOfAccumulatedOtherComprehensiveIncomeLineItems_A8F60B6557690359AA1742AB11B45B1B" xlink:to="loc_us-gaap_LaborAndRelatedExpense_7A84D9207EB08AF3365742AB11B5243E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OtherNoninterestExpense" xlink:label="loc_us-gaap_OtherNoninterestExpense_C540C9E3E05D08232CF242AB11B5D10E" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ReclassificationAdjustmentOutOfAccumulatedOtherComprehensiveIncomeLineItems_A8F60B6557690359AA1742AB11B45B1B" xlink:to="loc_us-gaap_OtherNoninterestExpense_C540C9E3E05D08232CF242AB11B5D10E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessCombinationAcquisitionRelatedCosts" xlink:label="loc_us-gaap_BusinessCombinationAcquisitionRelatedCosts_99283EBD6424BF2B502242AB11B5C4B4" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ReclassificationAdjustmentOutOfAccumulatedOtherComprehensiveIncomeLineItems_A8F60B6557690359AA1742AB11B45B1B" xlink:to="loc_us-gaap_BusinessCombinationAcquisitionRelatedCosts_99283EBD6424BF2B502242AB11B5C4B4" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_IncomeLossFromContinuingOperationsIncludingPortionAttributableToNoncontrollingInterest" xlink:label="loc_us-gaap_IncomeLossFromContinuingOperationsIncludingPortionAttributableToNoncontrollingInterest_5EAC0503B46514979A1942AB11B55438" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ReclassificationAdjustmentOutOfAccumulatedOtherComprehensiveIncomeLineItems_A8F60B6557690359AA1742AB11B45B1B" xlink:to="loc_us-gaap_IncomeLossFromContinuingOperationsIncludingPortionAttributableToNoncontrollingInterest_5EAC0503B46514979A1942AB11B55438" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_IncomeTaxExpenseBenefit" xlink:label="loc_us-gaap_IncomeTaxExpenseBenefit_37827524EEE4936B472642AB11B5FD0F" xlink:type="locator" />
    <link:definitionArc order="8" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ReclassificationAdjustmentOutOfAccumulatedOtherComprehensiveIncomeLineItems_A8F60B6557690359AA1742AB11B45B1B" xlink:to="loc_us-gaap_IncomeTaxExpenseBenefit_37827524EEE4936B472642AB11B5FD0F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic" xlink:label="loc_us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic_5AE3308F7A50D0D792EE42AB11B6C232" xlink:type="locator" />
    <link:definitionArc order="9" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ReclassificationAdjustmentOutOfAccumulatedOtherComprehensiveIncomeLineItems_A8F60B6557690359AA1742AB11B45B1B" xlink:to="loc_us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic_5AE3308F7A50D0D792EE42AB11B6C232" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://ucbi.com/role/ReclassificationsOutOfAccumulatedOtherComprehensiveIncomeTables" xlink:type="extended" />
  <link:definitionLink xlink:role="http://ucbi.com/role/Securities" xlink:type="extended" />
  <link:definitionLink xlink:role="http://ucbi.com/role/SecuritiesAmortizedCostAndFairValueOfHeldToMaturityAndAvailableForSaleSecuritiesByContractualMaturityDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ScheduleOfTradingSecuritiesAndOtherTradingAssetsLineItems" xlink:label="loc_us-gaap_ScheduleOfTradingSecuritiesAndOtherTradingAssetsLineItems_54A7F18BCEAA58F3A22036E3BF9D1A1A" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ScheduleOfTradingSecuritiesAndOtherTradingAssetsTable" xlink:label="loc_us-gaap_ScheduleOfTradingSecuritiesAndOtherTradingAssetsTable_24A2FD96368B52E98FBB29E4FD24A5C9" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ScheduleOfTradingSecuritiesAndOtherTradingAssetsLineItems_54A7F18BCEAA58F3A22036E3BF9D1A1A" xlink:to="loc_us-gaap_ScheduleOfTradingSecuritiesAndOtherTradingAssetsTable_24A2FD96368B52E98FBB29E4FD24A5C9" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FinancialInstrumentAxis" xlink:label="loc_us-gaap_FinancialInstrumentAxis_2ED961EA56B158D9A24F9F0C12805E97" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfTradingSecuritiesAndOtherTradingAssetsTable_24A2FD96368B52E98FBB29E4FD24A5C9" xlink:to="loc_us-gaap_FinancialInstrumentAxis_2ED961EA56B158D9A24F9F0C12805E97" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_D2FF95FC0673986C7B5CF8CC4BFDEF93_3639CE68F660501A8F4042849B1BEF0D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_2ED961EA56B158D9A24F9F0C12805E97" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_D2FF95FC0673986C7B5CF8CC4BFDEF93_3639CE68F660501A8F4042849B1BEF0D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_C818E6F0F1725AC5AEBF2FC27F2C1EC1" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_2ED961EA56B158D9A24F9F0C12805E97" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_C818E6F0F1725AC5AEBF2FC27F2C1EC1" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_USTreasurySecuritiesMember" xlink:label="loc_us-gaap_USTreasurySecuritiesMember_85DEBEDC44FF5430B6E6ADC1C3338056" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_C818E6F0F1725AC5AEBF2FC27F2C1EC1" xlink:to="loc_us-gaap_USTreasurySecuritiesMember_85DEBEDC44FF5430B6E6ADC1C3338056" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_USGovernmentAgenciesDebtSecuritiesMember" xlink:label="loc_us-gaap_USGovernmentAgenciesDebtSecuritiesMember_23C41130204B59BFA0D76C9BF0FCA00B" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_C818E6F0F1725AC5AEBF2FC27F2C1EC1" xlink:to="loc_us-gaap_USGovernmentAgenciesDebtSecuritiesMember_23C41130204B59BFA0D76C9BF0FCA00B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_USStatesAndPoliticalSubdivisionsMember" xlink:label="loc_us-gaap_USStatesAndPoliticalSubdivisionsMember_76D8A27E66C55E7BAC9AB2D36CF5CD35" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_C818E6F0F1725AC5AEBF2FC27F2C1EC1" xlink:to="loc_us-gaap_USStatesAndPoliticalSubdivisionsMember_76D8A27E66C55E7BAC9AB2D36CF5CD35" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CorporateDebtSecuritiesMember" xlink:label="loc_us-gaap_CorporateDebtSecuritiesMember_9C93BAA66FD756889F3F7D2BE3EDD02B" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_C818E6F0F1725AC5AEBF2FC27F2C1EC1" xlink:to="loc_us-gaap_CorporateDebtSecuritiesMember_9C93BAA66FD756889F3F7D2BE3EDD02B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AssetBackedSecuritiesMember" xlink:label="loc_us-gaap_AssetBackedSecuritiesMember_B47DA1AAFA4F592183D1E2AD8EC84C64" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_C818E6F0F1725AC5AEBF2FC27F2C1EC1" xlink:to="loc_us-gaap_AssetBackedSecuritiesMember_B47DA1AAFA4F592183D1E2AD8EC84C64" xlink:type="arc" />
    <link:loc xlink:href="ucbi-20190930.xsd#ucbi_SecuritiesOtherThanMortgageBackedSecuritiesMember" xlink:label="loc_ucbi_SecuritiesOtherThanMortgageBackedSecuritiesMember_5C7B48A656695316B2CA12B5F6B23514" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_C818E6F0F1725AC5AEBF2FC27F2C1EC1" xlink:to="loc_ucbi_SecuritiesOtherThanMortgageBackedSecuritiesMember_5C7B48A656695316B2CA12B5F6B23514" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ResidentialMortgageBackedSecuritiesMember" xlink:label="loc_us-gaap_ResidentialMortgageBackedSecuritiesMember_55A2E12E6B56578096414FD0DB86B0E7" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_C818E6F0F1725AC5AEBF2FC27F2C1EC1" xlink:to="loc_us-gaap_ResidentialMortgageBackedSecuritiesMember_55A2E12E6B56578096414FD0DB86B0E7" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CommercialMortgageBackedSecuritiesMember" xlink:label="loc_us-gaap_CommercialMortgageBackedSecuritiesMember_ED2AD73BE41E50339900B828FEE361DB" xlink:type="locator" />
    <link:definitionArc order="8" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_C818E6F0F1725AC5AEBF2FC27F2C1EC1" xlink:to="loc_us-gaap_CommercialMortgageBackedSecuritiesMember_ED2AD73BE41E50339900B828FEE361DB" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAmortizedCostBasisRollingMaturityAbstract" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAmortizedCostBasisRollingMaturityAbstract_EA5A719E5E6E5EED905AE25A5E1EDD45" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfTradingSecuritiesAndOtherTradingAssetsLineItems_54A7F18BCEAA58F3A22036E3BF9D1A1A" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAmortizedCostBasisRollingMaturityAbstract_EA5A719E5E6E5EED905AE25A5E1EDD45" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AvailableForSaleSecuritiesDebtMaturitiesNextRollingTwelveMonthsAmortizedCostBasis" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesNextRollingTwelveMonthsAmortizedCostBasis_9CE0F8417E6E5DCA936A19266CC3614F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAmortizedCostBasisRollingMaturityAbstract_EA5A719E5E6E5EED905AE25A5E1EDD45" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesNextRollingTwelveMonthsAmortizedCostBasis_9CE0F8417E6E5DCA936A19266CC3614F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AvailableForSaleSecuritiesDebtMaturitiesRollingYearTwoThroughFiveAmortizedCostBasis" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesRollingYearTwoThroughFiveAmortizedCostBasis_8AEB797DFCDD5EBEB5B2D0A797575FC0" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAmortizedCostBasisRollingMaturityAbstract_EA5A719E5E6E5EED905AE25A5E1EDD45" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesRollingYearTwoThroughFiveAmortizedCostBasis_8AEB797DFCDD5EBEB5B2D0A797575FC0" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AvailableForSaleSecuritiesDebtMaturitiesRollingYearSixThroughTenAmortizedCostBasis" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesRollingYearSixThroughTenAmortizedCostBasis_4D4625B89D3E53578D9B8C38DF483329" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAmortizedCostBasisRollingMaturityAbstract_EA5A719E5E6E5EED905AE25A5E1EDD45" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesRollingYearSixThroughTenAmortizedCostBasis_4D4625B89D3E53578D9B8C38DF483329" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AvailableForSaleSecuritiesDebtMaturitiesRollingAfterYearTenAmortizedCostBasis" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesRollingAfterYearTenAmortizedCostBasis_98E27FFC4785560F9CD91595E25F2C7A" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAmortizedCostBasisRollingMaturityAbstract_EA5A719E5E6E5EED905AE25A5E1EDD45" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesRollingAfterYearTenAmortizedCostBasis_98E27FFC4785560F9CD91595E25F2C7A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis" xlink:label="loc_us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis_1AB36A38433B51B88F336FB90345FEB9" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAmortizedCostBasisRollingMaturityAbstract_EA5A719E5E6E5EED905AE25A5E1EDD45" xlink:to="loc_us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis_1AB36A38433B51B88F336FB90345FEB9" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AvailableForSaleSecuritiesDebtMaturitiesFairValueRollingMaturityAbstract" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesFairValueRollingMaturityAbstract_F0E7CF59CAFD5940864AFDA19E008448" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfTradingSecuritiesAndOtherTradingAssetsLineItems_54A7F18BCEAA58F3A22036E3BF9D1A1A" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesFairValueRollingMaturityAbstract_F0E7CF59CAFD5940864AFDA19E008448" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AvailableForSaleSecuritiesDebtMaturitiesNextRollingTwelveMonthsFairValue" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesNextRollingTwelveMonthsFairValue_FA7195E005245DFD86DA089A11F585B2" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesFairValueRollingMaturityAbstract_F0E7CF59CAFD5940864AFDA19E008448" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesNextRollingTwelveMonthsFairValue_FA7195E005245DFD86DA089A11F585B2" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AvailableForSaleSecuritiesDebtMaturitiesRollingYearTwoThroughFiveFairValue" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesRollingYearTwoThroughFiveFairValue_CC893BA2752C55B6A912BA04B9C0C1CD" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesFairValueRollingMaturityAbstract_F0E7CF59CAFD5940864AFDA19E008448" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesRollingYearTwoThroughFiveFairValue_CC893BA2752C55B6A912BA04B9C0C1CD" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AvailableForSaleSecuritiesDebtMaturitiesRollingYearSixThroughTenFairValue" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesRollingYearSixThroughTenFairValue_2FDC72FEA31C53E3A4C670E85BF0A0A5" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesFairValueRollingMaturityAbstract_F0E7CF59CAFD5940864AFDA19E008448" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesRollingYearSixThroughTenFairValue_2FDC72FEA31C53E3A4C670E85BF0A0A5" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AvailableForSaleSecuritiesDebtMaturitiesRollingAfterYearTenFairValue" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesRollingAfterYearTenFairValue_CA553C8CF13C5B7FAB8FE572FC992F11" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesFairValueRollingMaturityAbstract_F0E7CF59CAFD5940864AFDA19E008448" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesRollingAfterYearTenFairValue_CA553C8CF13C5B7FAB8FE572FC992F11" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AvailableForSaleSecuritiesDebtSecurities" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtSecurities_CE12D3B7F02F580186A43D1F893A05C2" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesFairValueRollingMaturityAbstract_F0E7CF59CAFD5940864AFDA19E008448" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtSecurities_CE12D3B7F02F580186A43D1F893A05C2" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_HeldToMaturitySecuritiesDebtMaturitiesNetCarryingAmountAbstract" xlink:label="loc_us-gaap_HeldToMaturitySecuritiesDebtMaturitiesNetCarryingAmountAbstract_9205FB1660A657C89214DA16509806EC" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfTradingSecuritiesAndOtherTradingAssetsLineItems_54A7F18BCEAA58F3A22036E3BF9D1A1A" xlink:to="loc_us-gaap_HeldToMaturitySecuritiesDebtMaturitiesNetCarryingAmountAbstract_9205FB1660A657C89214DA16509806EC" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_HeldToMaturitySecuritiesDebtMaturitiesWithinOneYearNetCarryingAmount" xlink:label="loc_us-gaap_HeldToMaturitySecuritiesDebtMaturitiesWithinOneYearNetCarryingAmount_2107E30F7FB658878639B8C46559FB47" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HeldToMaturitySecuritiesDebtMaturitiesNetCarryingAmountAbstract_9205FB1660A657C89214DA16509806EC" xlink:to="loc_us-gaap_HeldToMaturitySecuritiesDebtMaturitiesWithinOneYearNetCarryingAmount_2107E30F7FB658878639B8C46559FB47" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_HeldToMaturitySecuritiesDebtMaturitiesAfterOneThroughFiveYearsNetCarryingAmount" xlink:label="loc_us-gaap_HeldToMaturitySecuritiesDebtMaturitiesAfterOneThroughFiveYearsNetCarryingAmount_7949BD5D65AA5163A32CD1E3D536EABA" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HeldToMaturitySecuritiesDebtMaturitiesNetCarryingAmountAbstract_9205FB1660A657C89214DA16509806EC" xlink:to="loc_us-gaap_HeldToMaturitySecuritiesDebtMaturitiesAfterOneThroughFiveYearsNetCarryingAmount_7949BD5D65AA5163A32CD1E3D536EABA" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_HeldToMaturitySecuritiesDebtMaturitiesAfterFiveThroughTenYearsNetCarryingAmount" xlink:label="loc_us-gaap_HeldToMaturitySecuritiesDebtMaturitiesAfterFiveThroughTenYearsNetCarryingAmount_9FED1E74B2EC5A27B2045A1C5A1F7B93" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HeldToMaturitySecuritiesDebtMaturitiesNetCarryingAmountAbstract_9205FB1660A657C89214DA16509806EC" xlink:to="loc_us-gaap_HeldToMaturitySecuritiesDebtMaturitiesAfterFiveThroughTenYearsNetCarryingAmount_9FED1E74B2EC5A27B2045A1C5A1F7B93" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_HeldToMaturitySecuritiesDebtMaturitiesAfterTenYearsNetCarryingAmount" xlink:label="loc_us-gaap_HeldToMaturitySecuritiesDebtMaturitiesAfterTenYearsNetCarryingAmount_C990EC70B0125B6290DB11CF6B719A93" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HeldToMaturitySecuritiesDebtMaturitiesNetCarryingAmountAbstract_9205FB1660A657C89214DA16509806EC" xlink:to="loc_us-gaap_HeldToMaturitySecuritiesDebtMaturitiesAfterTenYearsNetCarryingAmount_C990EC70B0125B6290DB11CF6B719A93" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_HeldToMaturitySecuritiesAmortizedCostBeforeOtherThanTemporaryImpairment" xlink:label="loc_us-gaap_HeldToMaturitySecuritiesAmortizedCostBeforeOtherThanTemporaryImpairment_318B85CBC18A5EECA3A72A3F850A9D12" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HeldToMaturitySecuritiesDebtMaturitiesNetCarryingAmountAbstract_9205FB1660A657C89214DA16509806EC" xlink:to="loc_us-gaap_HeldToMaturitySecuritiesAmortizedCostBeforeOtherThanTemporaryImpairment_318B85CBC18A5EECA3A72A3F850A9D12" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_HeldToMaturitySecuritiesDebtMaturitiesFairValueRollingMaturityAbstract" xlink:label="loc_us-gaap_HeldToMaturitySecuritiesDebtMaturitiesFairValueRollingMaturityAbstract_3A58E93C651E5E81BFF428C10767E7A5" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfTradingSecuritiesAndOtherTradingAssetsLineItems_54A7F18BCEAA58F3A22036E3BF9D1A1A" xlink:to="loc_us-gaap_HeldToMaturitySecuritiesDebtMaturitiesFairValueRollingMaturityAbstract_3A58E93C651E5E81BFF428C10767E7A5" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_HeldToMaturitySecuritiesDebtMaturitiesNextRollingTwelveMonthsFairValue" xlink:label="loc_us-gaap_HeldToMaturitySecuritiesDebtMaturitiesNextRollingTwelveMonthsFairValue_D1B23997B0695973ABAB88C4907A8B19" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HeldToMaturitySecuritiesDebtMaturitiesFairValueRollingMaturityAbstract_3A58E93C651E5E81BFF428C10767E7A5" xlink:to="loc_us-gaap_HeldToMaturitySecuritiesDebtMaturitiesNextRollingTwelveMonthsFairValue_D1B23997B0695973ABAB88C4907A8B19" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_HeldToMaturitySecuritiesDebtMaturitiesRollingYearTwoThroughFiveFairValue" xlink:label="loc_us-gaap_HeldToMaturitySecuritiesDebtMaturitiesRollingYearTwoThroughFiveFairValue_38D638085E885888B386DE2C435B1759" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HeldToMaturitySecuritiesDebtMaturitiesFairValueRollingMaturityAbstract_3A58E93C651E5E81BFF428C10767E7A5" xlink:to="loc_us-gaap_HeldToMaturitySecuritiesDebtMaturitiesRollingYearTwoThroughFiveFairValue_38D638085E885888B386DE2C435B1759" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_HeldToMaturitySecuritiesDebtMaturitiesRollingYearSixThroughTenFairValue" xlink:label="loc_us-gaap_HeldToMaturitySecuritiesDebtMaturitiesRollingYearSixThroughTenFairValue_2B214A02151D5A3DBB50B4C70EA486D4" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HeldToMaturitySecuritiesDebtMaturitiesFairValueRollingMaturityAbstract_3A58E93C651E5E81BFF428C10767E7A5" xlink:to="loc_us-gaap_HeldToMaturitySecuritiesDebtMaturitiesRollingYearSixThroughTenFairValue_2B214A02151D5A3DBB50B4C70EA486D4" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_HeldToMaturitySecuritiesDebtMaturitiesRollingAfterTenYearsFairValue" xlink:label="loc_us-gaap_HeldToMaturitySecuritiesDebtMaturitiesRollingAfterTenYearsFairValue_542191A68B86595887B599AE8E1B75DC" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HeldToMaturitySecuritiesDebtMaturitiesFairValueRollingMaturityAbstract_3A58E93C651E5E81BFF428C10767E7A5" xlink:to="loc_us-gaap_HeldToMaturitySecuritiesDebtMaturitiesRollingAfterTenYearsFairValue_542191A68B86595887B599AE8E1B75DC" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_HeldToMaturitySecuritiesFairValue" xlink:label="loc_us-gaap_HeldToMaturitySecuritiesFairValue_14D4BC7235825901B166AD19724D6909" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HeldToMaturitySecuritiesDebtMaturitiesFairValueRollingMaturityAbstract_3A58E93C651E5E81BFF428C10767E7A5" xlink:to="loc_us-gaap_HeldToMaturitySecuritiesFairValue_14D4BC7235825901B166AD19724D6909" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://ucbi.com/role/SecuritiesAmortizedCostGrossUnrealizedGainsAndLossesAndFairValueOfDebtSecuritiesAvailableForSaleDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems" xlink:label="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_BDD4AF2AAFA555BFB97ADF7C2B01F212" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ScheduleOfAvailableForSaleSecuritiesTable" xlink:label="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesTable_7C99DCEE79155D9BB72D8194D52A091F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_BDD4AF2AAFA555BFB97ADF7C2B01F212" xlink:to="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesTable_7C99DCEE79155D9BB72D8194D52A091F" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FinancialInstrumentAxis" xlink:label="loc_us-gaap_FinancialInstrumentAxis_DA58808AB69F585AA808F452879392C9" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesTable_7C99DCEE79155D9BB72D8194D52A091F" xlink:to="loc_us-gaap_FinancialInstrumentAxis_DA58808AB69F585AA808F452879392C9" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_40E650FF31BE9DBD6410F8CC4C231A2A_3639CE68F660501A8F4042849B1BEF0D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_DA58808AB69F585AA808F452879392C9" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_40E650FF31BE9DBD6410F8CC4C231A2A_3639CE68F660501A8F4042849B1BEF0D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_CFD61A37AF2F56BD97BD7AA97D718E45" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_DA58808AB69F585AA808F452879392C9" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_CFD61A37AF2F56BD97BD7AA97D718E45" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_USTreasurySecuritiesMember" xlink:label="loc_us-gaap_USTreasurySecuritiesMember_3A5DE371F4295D7F8F7355F23177C11D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_CFD61A37AF2F56BD97BD7AA97D718E45" xlink:to="loc_us-gaap_USTreasurySecuritiesMember_3A5DE371F4295D7F8F7355F23177C11D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_USGovernmentAgenciesDebtSecuritiesMember" xlink:label="loc_us-gaap_USGovernmentAgenciesDebtSecuritiesMember_4EBBD98E05F25702A6E54FC380B8F434" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_CFD61A37AF2F56BD97BD7AA97D718E45" xlink:to="loc_us-gaap_USGovernmentAgenciesDebtSecuritiesMember_4EBBD98E05F25702A6E54FC380B8F434" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_USStatesAndPoliticalSubdivisionsMember" xlink:label="loc_us-gaap_USStatesAndPoliticalSubdivisionsMember_210229BCB03656118104FEAE2CC85098" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_CFD61A37AF2F56BD97BD7AA97D718E45" xlink:to="loc_us-gaap_USStatesAndPoliticalSubdivisionsMember_210229BCB03656118104FEAE2CC85098" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ResidentialMortgageBackedSecuritiesMember" xlink:label="loc_us-gaap_ResidentialMortgageBackedSecuritiesMember_975786D466ED54DCB131A286E18A1A6F" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_CFD61A37AF2F56BD97BD7AA97D718E45" xlink:to="loc_us-gaap_ResidentialMortgageBackedSecuritiesMember_975786D466ED54DCB131A286E18A1A6F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CommercialMortgageBackedSecuritiesMember" xlink:label="loc_us-gaap_CommercialMortgageBackedSecuritiesMember_3F3FA41DAA71504DB35044404A8574C1" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_CFD61A37AF2F56BD97BD7AA97D718E45" xlink:to="loc_us-gaap_CommercialMortgageBackedSecuritiesMember_3F3FA41DAA71504DB35044404A8574C1" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CorporateDebtSecuritiesMember" xlink:label="loc_us-gaap_CorporateDebtSecuritiesMember_60706F0DEB3858D789C2C8954ECFBA94" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_CFD61A37AF2F56BD97BD7AA97D718E45" xlink:to="loc_us-gaap_CorporateDebtSecuritiesMember_60706F0DEB3858D789C2C8954ECFBA94" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AssetBackedSecuritiesMember" xlink:label="loc_us-gaap_AssetBackedSecuritiesMember_AEA62F1104A95A5AA73F498898745D90" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_CFD61A37AF2F56BD97BD7AA97D718E45" xlink:to="loc_us-gaap_AssetBackedSecuritiesMember_AEA62F1104A95A5AA73F498898745D90" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AvailableForSaleSecuritiesAbstract" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesAbstract_1C0E73372A425AE8AE940E062994DB93" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_BDD4AF2AAFA555BFB97ADF7C2B01F212" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesAbstract_1C0E73372A425AE8AE940E062994DB93" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis" xlink:label="loc_us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis_40172A3457405B1C85221C02A8AF2C05" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesAbstract_1C0E73372A425AE8AE940E062994DB93" xlink:to="loc_us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis_40172A3457405B1C85221C02A8AF2C05" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax" xlink:label="loc_us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax_07AF6D396FE3520D81ABAD26CAE2E208" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesAbstract_1C0E73372A425AE8AE940E062994DB93" xlink:to="loc_us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax_07AF6D396FE3520D81ABAD26CAE2E208" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax" xlink:label="loc_us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax_AFA83F50F18455A0B13D87025DDDF328" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesAbstract_1C0E73372A425AE8AE940E062994DB93" xlink:to="loc_us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax_AFA83F50F18455A0B13D87025DDDF328" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AvailableForSaleSecuritiesDebtSecurities" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtSecurities_B47B95BA48565E4FBB5E7F394F23F2FC" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesAbstract_1C0E73372A425AE8AE940E062994DB93" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtSecurities_B47B95BA48565E4FBB5E7F394F23F2FC" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://ucbi.com/role/SecuritiesAmortizedCostGrossUnrealizedGainsAndLossesAndFairValueOfDebtSecuritiesHeldToMaturityDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ScheduleOfHeldToMaturitySecuritiesLineItems" xlink:label="loc_us-gaap_ScheduleOfHeldToMaturitySecuritiesLineItems_08FF25B86FDF53AA89477D8B1B4D44E1" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ScheduleOfHeldToMaturitySecuritiesTable" xlink:label="loc_us-gaap_ScheduleOfHeldToMaturitySecuritiesTable_7109A415E00A5DC18EE9C33C6E5B0E18" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ScheduleOfHeldToMaturitySecuritiesLineItems_08FF25B86FDF53AA89477D8B1B4D44E1" xlink:to="loc_us-gaap_ScheduleOfHeldToMaturitySecuritiesTable_7109A415E00A5DC18EE9C33C6E5B0E18" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FinancialInstrumentAxis" xlink:label="loc_us-gaap_FinancialInstrumentAxis_E66F092917ED58AE8E2BB54DC6161732" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfHeldToMaturitySecuritiesTable_7109A415E00A5DC18EE9C33C6E5B0E18" xlink:to="loc_us-gaap_FinancialInstrumentAxis_E66F092917ED58AE8E2BB54DC6161732" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_C84EB9063818BAFA0E1DF8CC4C2AD28C_3639CE68F660501A8F4042849B1BEF0D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_E66F092917ED58AE8E2BB54DC6161732" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_C84EB9063818BAFA0E1DF8CC4C2AD28C_3639CE68F660501A8F4042849B1BEF0D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_DA0BEB731C99549092371872910D123B" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_E66F092917ED58AE8E2BB54DC6161732" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_DA0BEB731C99549092371872910D123B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_USStatesAndPoliticalSubdivisionsMember" xlink:label="loc_us-gaap_USStatesAndPoliticalSubdivisionsMember_E374B3B05FC258D9B66243353EFF1E6B" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_DA0BEB731C99549092371872910D123B" xlink:to="loc_us-gaap_USStatesAndPoliticalSubdivisionsMember_E374B3B05FC258D9B66243353EFF1E6B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ResidentialMortgageBackedSecuritiesMember" xlink:label="loc_us-gaap_ResidentialMortgageBackedSecuritiesMember_991E26FE608851E69FD58B4989B27649" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_DA0BEB731C99549092371872910D123B" xlink:to="loc_us-gaap_ResidentialMortgageBackedSecuritiesMember_991E26FE608851E69FD58B4989B27649" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CommercialMortgageBackedSecuritiesMember" xlink:label="loc_us-gaap_CommercialMortgageBackedSecuritiesMember_0A0CC60A40405AF488D40E1B94716A0F" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_DA0BEB731C99549092371872910D123B" xlink:to="loc_us-gaap_CommercialMortgageBackedSecuritiesMember_0A0CC60A40405AF488D40E1B94716A0F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_HeldToMaturitySecuritiesAbstract" xlink:label="loc_us-gaap_HeldToMaturitySecuritiesAbstract_35532CE009A35B7381CB63C8DB685587" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfHeldToMaturitySecuritiesLineItems_08FF25B86FDF53AA89477D8B1B4D44E1" xlink:to="loc_us-gaap_HeldToMaturitySecuritiesAbstract_35532CE009A35B7381CB63C8DB685587" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_HeldToMaturitySecuritiesAmortizedCostBeforeOtherThanTemporaryImpairment" xlink:label="loc_us-gaap_HeldToMaturitySecuritiesAmortizedCostBeforeOtherThanTemporaryImpairment_A8CC5371A31755AAB799662F9B1BE5AD" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HeldToMaturitySecuritiesAbstract_35532CE009A35B7381CB63C8DB685587" xlink:to="loc_us-gaap_HeldToMaturitySecuritiesAmortizedCostBeforeOtherThanTemporaryImpairment_A8CC5371A31755AAB799662F9B1BE5AD" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingGain" xlink:label="loc_us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingGain_0C720AC4A89B5ED8923DABA4918F1AFA" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HeldToMaturitySecuritiesAbstract_35532CE009A35B7381CB63C8DB685587" xlink:to="loc_us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingGain_0C720AC4A89B5ED8923DABA4918F1AFA" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingLoss" xlink:label="loc_us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingLoss_9A1305C011D857CB94767F0C6B192D6D" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HeldToMaturitySecuritiesAbstract_35532CE009A35B7381CB63C8DB685587" xlink:to="loc_us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingLoss_9A1305C011D857CB94767F0C6B192D6D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_HeldToMaturitySecuritiesFairValue" xlink:label="loc_us-gaap_HeldToMaturitySecuritiesFairValue_602E514808E559FBB0F36FB32AD4646C" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HeldToMaturitySecuritiesAbstract_35532CE009A35B7381CB63C8DB685587" xlink:to="loc_us-gaap_HeldToMaturitySecuritiesFairValue_602E514808E559FBB0F36FB32AD4646C" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://ucbi.com/role/SecuritiesNarrativeDetails" xlink:type="extended" />
  <link:definitionLink xlink:role="http://ucbi.com/role/SecuritiesSummaryOfAvailableForSaleSecuritiesSalesActivityDetails" xlink:type="extended" />
  <link:definitionLink xlink:role="http://ucbi.com/role/SecuritiesSummaryOfDebtSecuritesHeldToMaturityInUnrealizedLossPositionDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ScheduleOfHeldToMaturitySecuritiesLineItems" xlink:label="loc_us-gaap_ScheduleOfHeldToMaturitySecuritiesLineItems_3D8E5B702F8750BB82381C9EC6981AD6" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ScheduleOfHeldToMaturitySecuritiesTable" xlink:label="loc_us-gaap_ScheduleOfHeldToMaturitySecuritiesTable_2106B8B899F7505793AEFE264DEC564D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ScheduleOfHeldToMaturitySecuritiesLineItems_3D8E5B702F8750BB82381C9EC6981AD6" xlink:to="loc_us-gaap_ScheduleOfHeldToMaturitySecuritiesTable_2106B8B899F7505793AEFE264DEC564D" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FinancialInstrumentAxis" xlink:label="loc_us-gaap_FinancialInstrumentAxis_E93D46570CBC5A1FA3395DD96076D490" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfHeldToMaturitySecuritiesTable_2106B8B899F7505793AEFE264DEC564D" xlink:to="loc_us-gaap_FinancialInstrumentAxis_E93D46570CBC5A1FA3395DD96076D490" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_4556D502D3D2487FD4A9F8CC4C18223E_3639CE68F660501A8F4042849B1BEF0D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_E93D46570CBC5A1FA3395DD96076D490" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_4556D502D3D2487FD4A9F8CC4C18223E_3639CE68F660501A8F4042849B1BEF0D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_38D2DEB1D92D50E2BB48E4C33F733E70" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_E93D46570CBC5A1FA3395DD96076D490" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_38D2DEB1D92D50E2BB48E4C33F733E70" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_USStatesAndPoliticalSubdivisionsMember" xlink:label="loc_us-gaap_USStatesAndPoliticalSubdivisionsMember_70A34A377D99554DAC6EB07E8B91D717" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_38D2DEB1D92D50E2BB48E4C33F733E70" xlink:to="loc_us-gaap_USStatesAndPoliticalSubdivisionsMember_70A34A377D99554DAC6EB07E8B91D717" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ResidentialMortgageBackedSecuritiesMember" xlink:label="loc_us-gaap_ResidentialMortgageBackedSecuritiesMember_BB45995CE0FA58C0B499DDF6ED0D3B33" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_38D2DEB1D92D50E2BB48E4C33F733E70" xlink:to="loc_us-gaap_ResidentialMortgageBackedSecuritiesMember_BB45995CE0FA58C0B499DDF6ED0D3B33" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CommercialMortgageBackedSecuritiesMember" xlink:label="loc_us-gaap_CommercialMortgageBackedSecuritiesMember_8E97C869CDE854369DE66AB3940532B7" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_38D2DEB1D92D50E2BB48E4C33F733E70" xlink:to="loc_us-gaap_CommercialMortgageBackedSecuritiesMember_8E97C869CDE854369DE66AB3940532B7" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionAbstract" xlink:label="loc_us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionAbstract_ABE9AE1F97BD5676871070EFC8A74A60" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfHeldToMaturitySecuritiesLineItems_3D8E5B702F8750BB82381C9EC6981AD6" xlink:to="loc_us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionAbstract_ABE9AE1F97BD5676871070EFC8A74A60" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue" xlink:label="loc_us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue_5CFAE018A1295FCBAEFB19C421D91B77" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionAbstract_ABE9AE1F97BD5676871070EFC8A74A60" xlink:to="loc_us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue_5CFAE018A1295FCBAEFB19C421D91B77" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss" xlink:label="loc_us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss_12F2D6B52BA259E0850A9703B5D7E56E" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionAbstract_ABE9AE1F97BD5676871070EFC8A74A60" xlink:to="loc_us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss_12F2D6B52BA259E0850A9703B5D7E56E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue" xlink:label="loc_us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue_8FEE2595E263562FB1D2C74B65482CAB" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionAbstract_ABE9AE1F97BD5676871070EFC8A74A60" xlink:to="loc_us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue_8FEE2595E263562FB1D2C74B65482CAB" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss" xlink:label="loc_us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss_1E2075D7763A5363A4639F35F149575C" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionAbstract_ABE9AE1F97BD5676871070EFC8A74A60" xlink:to="loc_us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss_1E2075D7763A5363A4639F35F149575C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionFairValue" xlink:label="loc_us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionFairValue_85D45EBD13965019ABD44FEB1CAFCCA1" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionAbstract_ABE9AE1F97BD5676871070EFC8A74A60" xlink:to="loc_us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionFairValue_85D45EBD13965019ABD44FEB1CAFCCA1" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionAccumulatedLoss" xlink:label="loc_us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionAccumulatedLoss_CA1A66886CFE5FCFBF83121D2A788579" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionAbstract_ABE9AE1F97BD5676871070EFC8A74A60" xlink:to="loc_us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionAccumulatedLoss_CA1A66886CFE5FCFBF83121D2A788579" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://ucbi.com/role/SecuritiesSummaryOfDebtSecuritiesAvailableForSaleInUnrealizedLossPositionDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems" xlink:label="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_E81F762F4FC758958FA9A03C4882A89D" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ScheduleOfAvailableForSaleSecuritiesTable" xlink:label="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesTable_4B0CC1EACDAC542493D749C1C3EF2562" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_E81F762F4FC758958FA9A03C4882A89D" xlink:to="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesTable_4B0CC1EACDAC542493D749C1C3EF2562" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FinancialInstrumentAxis" xlink:label="loc_us-gaap_FinancialInstrumentAxis_23C7AA2AC58D599A9DA44B0F20F88942" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesTable_4B0CC1EACDAC542493D749C1C3EF2562" xlink:to="loc_us-gaap_FinancialInstrumentAxis_23C7AA2AC58D599A9DA44B0F20F88942" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_C987FB5DB7F568855BA3F8CC4C0F5E42_3639CE68F660501A8F4042849B1BEF0D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_23C7AA2AC58D599A9DA44B0F20F88942" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_C987FB5DB7F568855BA3F8CC4C0F5E42_3639CE68F660501A8F4042849B1BEF0D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_B8DE5405D6DE569FAE3B0B6B1C5743FA" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_23C7AA2AC58D599A9DA44B0F20F88942" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_B8DE5405D6DE569FAE3B0B6B1C5743FA" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_USTreasurySecuritiesMember" xlink:label="loc_us-gaap_USTreasurySecuritiesMember_A32D9BE01C315989809D96C5AC332667" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_B8DE5405D6DE569FAE3B0B6B1C5743FA" xlink:to="loc_us-gaap_USTreasurySecuritiesMember_A32D9BE01C315989809D96C5AC332667" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_USGovernmentAgenciesDebtSecuritiesMember" xlink:label="loc_us-gaap_USGovernmentAgenciesDebtSecuritiesMember_DDA24007215F5635B32D3966E7D9B7FF" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_B8DE5405D6DE569FAE3B0B6B1C5743FA" xlink:to="loc_us-gaap_USGovernmentAgenciesDebtSecuritiesMember_DDA24007215F5635B32D3966E7D9B7FF" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_USStatesAndPoliticalSubdivisionsMember" xlink:label="loc_us-gaap_USStatesAndPoliticalSubdivisionsMember_D6337C82667A54BA8A9A1C29069EE476" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_B8DE5405D6DE569FAE3B0B6B1C5743FA" xlink:to="loc_us-gaap_USStatesAndPoliticalSubdivisionsMember_D6337C82667A54BA8A9A1C29069EE476" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ResidentialMortgageBackedSecuritiesMember" xlink:label="loc_us-gaap_ResidentialMortgageBackedSecuritiesMember_8D75A57D1E1653099A61AFD22E7B9B3C" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_B8DE5405D6DE569FAE3B0B6B1C5743FA" xlink:to="loc_us-gaap_ResidentialMortgageBackedSecuritiesMember_8D75A57D1E1653099A61AFD22E7B9B3C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CommercialMortgageBackedSecuritiesMember" xlink:label="loc_us-gaap_CommercialMortgageBackedSecuritiesMember_A036E03066735030B86927B3126288FB" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_B8DE5405D6DE569FAE3B0B6B1C5743FA" xlink:to="loc_us-gaap_CommercialMortgageBackedSecuritiesMember_A036E03066735030B86927B3126288FB" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CorporateDebtSecuritiesMember" xlink:label="loc_us-gaap_CorporateDebtSecuritiesMember_12B640A52DB25018B82F6AA8C82E4ADC" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_B8DE5405D6DE569FAE3B0B6B1C5743FA" xlink:to="loc_us-gaap_CorporateDebtSecuritiesMember_12B640A52DB25018B82F6AA8C82E4ADC" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AssetBackedSecuritiesMember" xlink:label="loc_us-gaap_AssetBackedSecuritiesMember_30BD49E965005F07B5BDE43103B95398" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_B8DE5405D6DE569FAE3B0B6B1C5743FA" xlink:to="loc_us-gaap_AssetBackedSecuritiesMember_30BD49E965005F07B5BDE43103B95398" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionAccumulatedLossAbstract" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionAccumulatedLossAbstract_0AAD08443C7A517BADEE203D505F9DB9" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_E81F762F4FC758958FA9A03C4882A89D" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionAccumulatedLossAbstract_0AAD08443C7A517BADEE203D505F9DB9" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12Months" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12Months_AE49B32AB17D50A383BAA866BA5F0D37" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionAccumulatedLossAbstract_0AAD08443C7A517BADEE203D505F9DB9" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12Months_AE49B32AB17D50A383BAA866BA5F0D37" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss_9B498F48BA025242A49D6B19067D66E3" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionAccumulatedLossAbstract_0AAD08443C7A517BADEE203D505F9DB9" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss_9B498F48BA025242A49D6B19067D66E3" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLonger" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLonger_47AF551E1D665F88A509C45D73CDD59B" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionAccumulatedLossAbstract_0AAD08443C7A517BADEE203D505F9DB9" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLonger_47AF551E1D665F88A509C45D73CDD59B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss_72FE1760C2A55BB4A46DD9BDF26E422D" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionAccumulatedLossAbstract_0AAD08443C7A517BADEE203D505F9DB9" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss_72FE1760C2A55BB4A46DD9BDF26E422D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtSecuritiesAvailableForSaleUnrealizedLossPosition" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleUnrealizedLossPosition_A093E81472E45E39AFE5955494254D8E" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionAccumulatedLossAbstract_0AAD08443C7A517BADEE203D505F9DB9" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleUnrealizedLossPosition_A093E81472E45E39AFE5955494254D8E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtSecuritiesAvailableForSaleUnrealizedLossPositionAccumulatedLoss" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleUnrealizedLossPositionAccumulatedLoss_4A76B72FB720516C8CEA323585C37442" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionAccumulatedLossAbstract_0AAD08443C7A517BADEE203D505F9DB9" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleUnrealizedLossPositionAccumulatedLoss_4A76B72FB720516C8CEA323585C37442" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://ucbi.com/role/SecuritiesTables" xlink:type="extended" />
  <link:definitionLink xlink:role="http://ucbi.com/role/StockBasedCompensation" xlink:type="extended" />
  <link:definitionLink xlink:role="http://ucbi.com/role/StockBasedCompensationNarrativeDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_65CA6AF56978DF9B903A39D0DE4A5BC6" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_BC959D17AB3D121A272D39D0DE3B195B" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_65CA6AF56978DF9B903A39D0DE4A5BC6" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_BC959D17AB3D121A272D39D0DE3B195B" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_IncomeStatementLocationAxis" xlink:label="loc_us-gaap_IncomeStatementLocationAxis_523BF008956D054E3FE139D0DE3BC0F7" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_BC959D17AB3D121A272D39D0DE3B195B" xlink:to="loc_us-gaap_IncomeStatementLocationAxis_523BF008956D054E3FE139D0DE3BC0F7" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_IncomeStatementLocationDomain" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_4FB3E57F25D82481272539D0DE3B6F69_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_523BF008956D054E3FE139D0DE3BC0F7" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_4FB3E57F25D82481272539D0DE3B6F69_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_IncomeStatementLocationDomain" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_4FB3E57F25D82481272539D0DE3B6F69" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_523BF008956D054E3FE139D0DE3BC0F7" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_4FB3E57F25D82481272539D0DE3B6F69" xlink:type="arc" />
    <link:loc xlink:href="ucbi-20190930.xsd#ucbi_MergerRelatedAndOtherCostsMember" xlink:label="loc_ucbi_MergerRelatedAndOtherCostsMember_7CF9E39F74536B21BDE539D0DE3BFDFF" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_4FB3E57F25D82481272539D0DE3B6F69" xlink:to="loc_ucbi_MergerRelatedAndOtherCostsMember_7CF9E39F74536B21BDE539D0DE3BFDFF" xlink:type="arc" />
    <link:loc xlink:href="ucbi-20190930.xsd#ucbi_CompensationExpenseMember" xlink:label="loc_ucbi_CompensationExpenseMember_E2AC46DDF6E8A415430E39D0DE3B8B40" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_4FB3E57F25D82481272539D0DE3B6F69" xlink:to="loc_ucbi_CompensationExpenseMember_E2AC46DDF6E8A415430E39D0DE3B8B40" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_TitleOfIndividualAxis" xlink:label="loc_srt_TitleOfIndividualAxis_D2483CA9E2C1ECDDF0B839D0DE3BD7FB" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_BC959D17AB3D121A272D39D0DE3B195B" xlink:to="loc_srt_TitleOfIndividualAxis_D2483CA9E2C1ECDDF0B839D0DE3BD7FB" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_TitleOfIndividualWithRelationshipToEntityDomain" xlink:label="loc_srt_TitleOfIndividualWithRelationshipToEntityDomain_9B8624C2717B9B45BC4839D0DE3B27B9_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_TitleOfIndividualAxis_D2483CA9E2C1ECDDF0B839D0DE3BD7FB" xlink:to="loc_srt_TitleOfIndividualWithRelationshipToEntityDomain_9B8624C2717B9B45BC4839D0DE3B27B9_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_TitleOfIndividualWithRelationshipToEntityDomain" xlink:label="loc_srt_TitleOfIndividualWithRelationshipToEntityDomain_9B8624C2717B9B45BC4839D0DE3B27B9" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_TitleOfIndividualAxis_D2483CA9E2C1ECDDF0B839D0DE3BD7FB" xlink:to="loc_srt_TitleOfIndividualWithRelationshipToEntityDomain_9B8624C2717B9B45BC4839D0DE3B27B9" xlink:type="arc" />
    <link:loc xlink:href="ucbi-20190930.xsd#ucbi_EmployeeMember" xlink:label="loc_ucbi_EmployeeMember_C344F202B533AB6B69A639D0DE4ADC56" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_TitleOfIndividualWithRelationshipToEntityDomain_9B8624C2717B9B45BC4839D0DE3B27B9" xlink:to="loc_ucbi_EmployeeMember_C344F202B533AB6B69A639D0DE4ADC56" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_DirectorMember" xlink:label="loc_srt_DirectorMember_26C6C733BA7B35BC14F739D0DE4A17E5" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_TitleOfIndividualWithRelationshipToEntityDomain_9B8624C2717B9B45BC4839D0DE3B27B9" xlink:to="loc_srt_DirectorMember_26C6C733BA7B35BC14F739D0DE4A17E5" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AwardTypeAxis" xlink:label="loc_us-gaap_AwardTypeAxis_65DA72C31ABA5C1969AD39D0DE4A2626" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_BC959D17AB3D121A272D39D0DE3B195B" xlink:to="loc_us-gaap_AwardTypeAxis_65DA72C31ABA5C1969AD39D0DE4A2626" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_A269619CC6251056D98939D0DE4A533B_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_65DA72C31ABA5C1969AD39D0DE4A2626" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_A269619CC6251056D98939D0DE4A533B_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_A269619CC6251056D98939D0DE4A533B" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_65DA72C31ABA5C1969AD39D0DE4A2626" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_A269619CC6251056D98939D0DE4A533B" xlink:type="arc" />
    <link:loc xlink:href="ucbi-20190930.xsd#ucbi_SharebasedPaymentArrangementAcquisitionRelatedPerformanceGrantMember" xlink:label="loc_ucbi_SharebasedPaymentArrangementAcquisitionRelatedPerformanceGrantMember_0EC5EE6D0199A5B6247E39D0DE4A31B0" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_A269619CC6251056D98939D0DE4A533B" xlink:to="loc_ucbi_SharebasedPaymentArrangementAcquisitionRelatedPerformanceGrantMember_0EC5EE6D0199A5B6247E39D0DE4A31B0" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_EmployeeStockOptionMember" xlink:label="loc_us-gaap_EmployeeStockOptionMember_755B99969622F360CB8639D0DE4AE758" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_A269619CC6251056D98939D0DE4A533B" xlink:to="loc_us-gaap_EmployeeStockOptionMember_755B99969622F360CB8639D0DE4AE758" xlink:type="arc" />
    <link:loc xlink:href="ucbi-20190930.xsd#ucbi_PerformanceBasedRestrictedStockUnitsMember" xlink:label="loc_ucbi_PerformanceBasedRestrictedStockUnitsMember_F736F7F94EB14BCEB71439D362803176" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_A269619CC6251056D98939D0DE4A533B" xlink:to="loc_ucbi_PerformanceBasedRestrictedStockUnitsMember_F736F7F94EB14BCEB71439D362803176" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RestrictedStockUnitsRSUMember" xlink:label="loc_us-gaap_RestrictedStockUnitsRSUMember_A92A309933EBA8EBBC3D39D0DE4A238C" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_A269619CC6251056D98939D0DE4A533B" xlink:to="loc_us-gaap_RestrictedStockUnitsRSUMember_A92A309933EBA8EBBC3D39D0DE4A238C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_RangeAxis" xlink:label="loc_srt_RangeAxis_76CA3076AFD9C6AC2C2E39D0DE4A2257" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_BC959D17AB3D121A272D39D0DE3B195B" xlink:to="loc_srt_RangeAxis_76CA3076AFD9C6AC2C2E39D0DE4A2257" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_RangeMember" xlink:label="loc_srt_RangeMember_C8D5D69599EF45B203C239D0DE4A2F95_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_76CA3076AFD9C6AC2C2E39D0DE4A2257" xlink:to="loc_srt_RangeMember_C8D5D69599EF45B203C239D0DE4A2F95_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_RangeMember" xlink:label="loc_srt_RangeMember_C8D5D69599EF45B203C239D0DE4A2F95" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_76CA3076AFD9C6AC2C2E39D0DE4A2257" xlink:to="loc_srt_RangeMember_C8D5D69599EF45B203C239D0DE4A2F95" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_MaximumMember" xlink:label="loc_srt_MaximumMember_2D187B91AA208095D19339D0DE4A8FF8" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_C8D5D69599EF45B203C239D0DE4A2F95" xlink:to="loc_srt_MaximumMember_2D187B91AA208095D19339D0DE4A8FF8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_A7A5137CFC868A1477A639D18A00F766" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_65CA6AF56978DF9B903A39D0DE4A5BC6" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_A7A5137CFC868A1477A639D18A00F766" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_B802BE28D185A896D35A39D1F856752B" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_65CA6AF56978DF9B903A39D0DE4A5BC6" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_B802BE28D185A896D35A39D1F856752B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1_7F75C778E6052CDC060D39D0DE4A1C3E" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_65CA6AF56978DF9B903A39D0DE4A5BC6" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1_7F75C778E6052CDC060D39D0DE4A1C3E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardExpirationPeriod" xlink:label="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardExpirationPeriod_A3B919D978CCD9DA08E439D0DE4A42C4" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_65CA6AF56978DF9B903A39D0DE4A5BC6" xlink:to="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardExpirationPeriod_A3B919D978CCD9DA08E439D0DE4A42C4" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant_6B1EF072B9C3ED8CE1C039D0DE4AFE57" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_65CA6AF56978DF9B903A39D0DE4A5BC6" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant_6B1EF072B9C3ED8CE1C039D0DE4AFE57" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross_46156A9228191CB1BA4E39D0DE4ABBD0" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_65CA6AF56978DF9B903A39D0DE4A5BC6" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross_46156A9228191CB1BA4E39D0DE4ABBD0" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AllocatedShareBasedCompensationExpense" xlink:label="loc_us-gaap_AllocatedShareBasedCompensationExpense_869134C40F51D12ED94439D0DE4AEA1A" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_65CA6AF56978DF9B903A39D0DE4A5BC6" xlink:to="loc_us-gaap_AllocatedShareBasedCompensationExpense_869134C40F51D12ED94439D0DE4AEA1A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAcceleratedCompensationCost" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAcceleratedCompensationCost_565E0937A26A492FC85F39D0DE4AF1DA" xlink:type="locator" />
    <link:definitionArc order="8" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_65CA6AF56978DF9B903A39D0DE4A5BC6" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAcceleratedCompensationCost_565E0937A26A492FC85F39D0DE4AF1DA" xlink:type="arc" />
    <link:loc xlink:href="ucbi-20190930.xsd#ucbi_ShareBasedCompensationArrangementByShareBasedPaymentAwardCostRelatedToAcquisition" xlink:label="loc_ucbi_ShareBasedCompensationArrangementByShareBasedPaymentAwardCostRelatedToAcquisition_8292D4C0B8A9422CD6CF39D0DE4A6984" xlink:type="locator" />
    <link:definitionArc order="9" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_65CA6AF56978DF9B903A39D0DE4A5BC6" xlink:to="loc_ucbi_ShareBasedCompensationArrangementByShareBasedPaymentAwardCostRelatedToAcquisition_8292D4C0B8A9422CD6CF39D0DE4A6984" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense_DC78CCCDE793B73D1BF239D0DE4AF9F9" xlink:type="locator" />
    <link:definitionArc order="10" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_65CA6AF56978DF9B903A39D0DE4A5BC6" xlink:to="loc_us-gaap_EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense_DC78CCCDE793B73D1BF239D0DE4AF9F9" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized_523445C4B6801D75253439D0DE4A96EA" xlink:type="locator" />
    <link:definitionArc order="11" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_65CA6AF56978DF9B903A39D0DE4A5BC6" xlink:to="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized_523445C4B6801D75253439D0DE4A96EA" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1_207AEFE84771E0CC335439D0DE4AC325" xlink:type="locator" />
    <link:definitionArc order="12" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_65CA6AF56978DF9B903A39D0DE4A5BC6" xlink:to="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1_207AEFE84771E0CC335439D0DE4AC325" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://ucbi.com/role/StockBasedCompensationRestrictedStockUnitActivityDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_3E4150E9FADF57A994376924988A1F93" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_82F0A0DB606C511DB2F8A40489FA125D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_3E4150E9FADF57A994376924988A1F93" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_82F0A0DB606C511DB2F8A40489FA125D" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AwardTypeAxis" xlink:label="loc_us-gaap_AwardTypeAxis_895B25F1684B5FB38615FFF3553AF6E4" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_82F0A0DB606C511DB2F8A40489FA125D" xlink:to="loc_us-gaap_AwardTypeAxis_895B25F1684B5FB38615FFF3553AF6E4" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_15D03B242E7D8CE02078F747E2961406_3639CE68F660501A8F4042849B1BEF0D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_895B25F1684B5FB38615FFF3553AF6E4" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_15D03B242E7D8CE02078F747E2961406_3639CE68F660501A8F4042849B1BEF0D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_A9AA2A9B4B225D6EA2CB37DBA7F06942" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_895B25F1684B5FB38615FFF3553AF6E4" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_A9AA2A9B4B225D6EA2CB37DBA7F06942" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RestrictedStockUnitsRSUMember" xlink:label="loc_us-gaap_RestrictedStockUnitsRSUMember_CA1B3DBCEDFF5F799DEA3421E3A06AEB" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_A9AA2A9B4B225D6EA2CB37DBA7F06942" xlink:to="loc_us-gaap_RestrictedStockUnitsRSUMember_CA1B3DBCEDFF5F799DEA3421E3A06AEB" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_057B229C33D650FCB4FE285DBA8FCB95" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_3E4150E9FADF57A994376924988A1F93" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_057B229C33D650FCB4FE285DBA8FCB95" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_AEF9649397DE543C941F4988A4C6AA5C" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_057B229C33D650FCB4FE285DBA8FCB95" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_AEF9649397DE543C941F4988A4C6AA5C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_9194AE66030F525ABBA8859DEB44E671" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_057B229C33D650FCB4FE285DBA8FCB95" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_9194AE66030F525ABBA8859DEB44E671" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_0DA0ECA0C5C05D819E525769E808407C" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_057B229C33D650FCB4FE285DBA8FCB95" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_0DA0ECA0C5C05D819E525769E808407C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod_FF6197A18C8855ACBA352F13EBE00420" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_057B229C33D650FCB4FE285DBA8FCB95" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod_FF6197A18C8855ACBA352F13EBE00420" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_30601911BFBD55268790A7D379E46EE1" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_3E4150E9FADF57A994376924988A1F93" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_30601911BFBD55268790A7D379E46EE1" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_64EE4DFD294A5CE0B7D4A6E027E86303" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_30601911BFBD55268790A7D379E46EE1" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_64EE4DFD294A5CE0B7D4A6E027E86303" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_7C30A7C761D65F0D9ADA6D600D17110E" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_30601911BFBD55268790A7D379E46EE1" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_7C30A7C761D65F0D9ADA6D600D17110E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue_2FB600986E725B73BD0832720FFDDD57" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_30601911BFBD55268790A7D379E46EE1" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue_2FB600986E725B73BD0832720FFDDD57" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue_E039A0E8241053F08812B2AAFC3CB6B7" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_30601911BFBD55268790A7D379E46EE1" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue_E039A0E8241053F08812B2AAFC3CB6B7" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsOutstandingWeightedAverageRemainingContractualTerms" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsOutstandingWeightedAverageRemainingContractualTerms_F1D507AB44BD55799394D5E4A6893587" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_3E4150E9FADF57A994376924988A1F93" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsOutstandingWeightedAverageRemainingContractualTerms_F1D507AB44BD55799394D5E4A6893587" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardEquityInstrumentsOtherThanOptionsAggregateIntrinsicValueVested" xlink:label="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardEquityInstrumentsOtherThanOptionsAggregateIntrinsicValueVested_954B7523769A55638C84F6F9F4174806" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_3E4150E9FADF57A994376924988A1F93" xlink:to="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardEquityInstrumentsOtherThanOptionsAggregateIntrinsicValueVested_954B7523769A55638C84F6F9F4174806" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardEquityInstrumentsOtherThanOptionsAggregateIntrinsicValueOutstanding" xlink:label="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardEquityInstrumentsOtherThanOptionsAggregateIntrinsicValueOutstanding_DEBCDE70DE885394A9E82F44459A6EE6" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_3E4150E9FADF57A994376924988A1F93" xlink:to="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardEquityInstrumentsOtherThanOptionsAggregateIntrinsicValueOutstanding_DEBCDE70DE885394A9E82F44459A6EE6" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://ucbi.com/role/StockBasedCompensationStockOptionActivityDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_68984496842F579D8AFB0B89EE660182" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_04C8ABA9116D5DE9A5B759EE0D996A69" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_68984496842F579D8AFB0B89EE660182" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_04C8ABA9116D5DE9A5B759EE0D996A69" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AwardTypeAxis" xlink:label="loc_us-gaap_AwardTypeAxis_4EE352EABF2F5ACABFFF9009B7FC11E0" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_04C8ABA9116D5DE9A5B759EE0D996A69" xlink:to="loc_us-gaap_AwardTypeAxis_4EE352EABF2F5ACABFFF9009B7FC11E0" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_91F5D193EE61C98E46A5F747E0BF044F_3639CE68F660501A8F4042849B1BEF0D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_4EE352EABF2F5ACABFFF9009B7FC11E0" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_91F5D193EE61C98E46A5F747E0BF044F_3639CE68F660501A8F4042849B1BEF0D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_16B517CC7294562B9D6E782F578A6250" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_4EE352EABF2F5ACABFFF9009B7FC11E0" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_16B517CC7294562B9D6E782F578A6250" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_EmployeeStockOptionMember" xlink:label="loc_us-gaap_EmployeeStockOptionMember_A32D98438B69556CBABF1265ECB94690" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_16B517CC7294562B9D6E782F578A6250" xlink:to="loc_us-gaap_EmployeeStockOptionMember_A32D98438B69556CBABF1265ECB94690" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingRollForward" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingRollForward_316EA175C25A56B0AD31D6F427D40BA2" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_68984496842F579D8AFB0B89EE660182" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingRollForward_316EA175C25A56B0AD31D6F427D40BA2" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber_35F84E686B1F5326914A191C0C0258DA" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingRollForward_316EA175C25A56B0AD31D6F427D40BA2" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber_35F84E686B1F5326914A191C0C0258DA" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised_F4759F37EC1E5FEC9A1101021409A42A" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingRollForward_316EA175C25A56B0AD31D6F427D40BA2" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised_F4759F37EC1E5FEC9A1101021409A42A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresInPeriod" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresInPeriod_96C06363B5CD5C5AA5B184AE06C15AAE" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingRollForward_316EA175C25A56B0AD31D6F427D40BA2" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresInPeriod_96C06363B5CD5C5AA5B184AE06C15AAE" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExpirationsInPeriod" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExpirationsInPeriod_EC14534B2A795181A84C8A8DAB4E6FA2" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingRollForward_316EA175C25A56B0AD31D6F427D40BA2" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExpirationsInPeriod_EC14534B2A795181A84C8A8DAB4E6FA2" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber_F0D89CE6FD4E5DE3BAC9E71375D47321" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingRollForward_316EA175C25A56B0AD31D6F427D40BA2" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber_F0D89CE6FD4E5DE3BAC9E71375D47321" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePriceRollforward" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePriceRollforward_14C16DAE215659DBBAA24C289EC74612" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_68984496842F579D8AFB0B89EE660182" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePriceRollforward_14C16DAE215659DBBAA24C289EC74612" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice_957F653E8C4152318F54588E121681A8" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePriceRollforward_14C16DAE215659DBBAA24C289EC74612" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice_957F653E8C4152318F54588E121681A8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice_A87CE960FD6355F5B46F2E80988A79F8" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePriceRollforward_14C16DAE215659DBBAA24C289EC74612" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice_A87CE960FD6355F5B46F2E80988A79F8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsForfeituresInPeriodWeightedAverageExercisePrice" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsForfeituresInPeriodWeightedAverageExercisePrice_6DC89F3CDA635F6CA50AA1069B99407E" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePriceRollforward_14C16DAE215659DBBAA24C289EC74612" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsForfeituresInPeriodWeightedAverageExercisePrice_6DC89F3CDA635F6CA50AA1069B99407E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExpirationsInPeriodWeightedAverageExercisePrice" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExpirationsInPeriodWeightedAverageExercisePrice_F9A729D97D2E589AA24390CC8D06A3B9" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePriceRollforward_14C16DAE215659DBBAA24C289EC74612" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExpirationsInPeriodWeightedAverageExercisePrice_F9A729D97D2E589AA24390CC8D06A3B9" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice_D77CD887600457DBA5880C8909C76B58" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePriceRollforward_14C16DAE215659DBBAA24C289EC74612" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice_D77CD887600457DBA5880C8909C76B58" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTerm2" xlink:label="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTerm2_93C600927C7C5FB5B3AFFE1CC20AF960" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_68984496842F579D8AFB0B89EE660182" xlink:to="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTerm2_93C600927C7C5FB5B3AFFE1CC20AF960" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableWeightedAverageRemainingContractualTerm1" xlink:label="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableWeightedAverageRemainingContractualTerm1_C1294944CEB45C509EA4C3AEFCF40FF7" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_68984496842F579D8AFB0B89EE660182" xlink:to="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableWeightedAverageRemainingContractualTerm1_C1294944CEB45C509EA4C3AEFCF40FF7" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue_F060F2CB53AA51E3ACE2DD55CB0EE820" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_68984496842F579D8AFB0B89EE660182" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue_F060F2CB53AA51E3ACE2DD55CB0EE820" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableIntrinsicValue1" xlink:label="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableIntrinsicValue1_AD4A2D6A021F51FE964FA345957B9302" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_68984496842F579D8AFB0B89EE660182" xlink:to="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableIntrinsicValue1_AD4A2D6A021F51FE964FA345957B9302" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://ucbi.com/role/StockBasedCompensationTables" xlink:type="extended" />
  <link:definitionLink xlink:role="http://ucbi.com/role/SubsequentEvents" xlink:type="extended" />
  <link:definitionLink xlink:role="http://ucbi.com/role/SubsequentEventsNarrativeDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SubsequentEventLineItems" xlink:label="loc_us-gaap_SubsequentEventLineItems_EF55F2D56E26923C901E42AB10B3BCF4" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SubsequentEventTable" xlink:label="loc_us-gaap_SubsequentEventTable_9FDB4DCD888F83C474D842AB10B1039E" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SubsequentEventLineItems_EF55F2D56E26923C901E42AB10B3BCF4" xlink:to="loc_us-gaap_SubsequentEventTable_9FDB4DCD888F83C474D842AB10B1039E" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SubsequentEventTypeAxis" xlink:label="loc_us-gaap_SubsequentEventTypeAxis_218B62F5B32A1D9C5ADB42AB10B251D7" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_SubsequentEventTable_9FDB4DCD888F83C474D842AB10B1039E" xlink:to="loc_us-gaap_SubsequentEventTypeAxis_218B62F5B32A1D9C5ADB42AB10B251D7" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SubsequentEventTypeDomain" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_62C93B36BDE7B16DDB8E42AB10B2C916_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_218B62F5B32A1D9C5ADB42AB10B251D7" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_62C93B36BDE7B16DDB8E42AB10B2C916_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SubsequentEventTypeDomain" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_62C93B36BDE7B16DDB8E42AB10B2C916" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_218B62F5B32A1D9C5ADB42AB10B251D7" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_62C93B36BDE7B16DDB8E42AB10B2C916" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SubsequentEventMember" xlink:label="loc_us-gaap_SubsequentEventMember_5E225726E7F38027EB9A42AB10B24733" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventTypeDomain_62C93B36BDE7B16DDB8E42AB10B2C916" xlink:to="loc_us-gaap_SubsequentEventMember_5E225726E7F38027EB9A42AB10B24733" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CommonStockDividendsPerShareDeclared" xlink:label="loc_us-gaap_CommonStockDividendsPerShareDeclared_08F37E5DAC40D451C32342AB10B38A98" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_EF55F2D56E26923C901E42AB10B3BCF4" xlink:to="loc_us-gaap_CommonStockDividendsPerShareDeclared_08F37E5DAC40D451C32342AB10B38A98" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DividendPayableDateToBePaidDayMonthAndYear" xlink:label="loc_us-gaap_DividendPayableDateToBePaidDayMonthAndYear_DF0A513770C6B5F0DEAA42AB10B3327F" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_EF55F2D56E26923C901E42AB10B3BCF4" xlink:to="loc_us-gaap_DividendPayableDateToBePaidDayMonthAndYear_DF0A513770C6B5F0DEAA42AB10B3327F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DividendsPayableDateOfRecordDayMonthAndYear" xlink:label="loc_us-gaap_DividendsPayableDateOfRecordDayMonthAndYear_59562BE865C8D323AB9042AB10B38DCB" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_EF55F2D56E26923C901E42AB10B3BCF4" xlink:to="loc_us-gaap_DividendsPayableDateOfRecordDayMonthAndYear_59562BE865C8D323AB9042AB10B38DCB" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://ucbi.com/role/TerminationOfDefinedBenefitPlanDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DefinedBenefitPlanDisclosureLineItems" xlink:label="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_DCBCA4C03B1D036AB9DB46F8C93AF9E1" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable" xlink:label="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_7A04443CD311BDC9B61B46F8C937ABC5" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_DCBCA4C03B1D036AB9DB46F8C93AF9E1" xlink:to="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_7A04443CD311BDC9B61B46F8C937ABC5" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RetirementPlanTypeAxis" xlink:label="loc_us-gaap_RetirementPlanTypeAxis_C9265E9D573AAFB8616046F8C9388E70" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_7A04443CD311BDC9B61B46F8C937ABC5" xlink:to="loc_us-gaap_RetirementPlanTypeAxis_C9265E9D573AAFB8616046F8C9388E70" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RetirementPlanTypeDomain" xlink:label="loc_us-gaap_RetirementPlanTypeDomain_30D29C21AE5A54C53C5C46F8C9388B3F_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RetirementPlanTypeAxis_C9265E9D573AAFB8616046F8C9388E70" xlink:to="loc_us-gaap_RetirementPlanTypeDomain_30D29C21AE5A54C53C5C46F8C9388B3F_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RetirementPlanTypeDomain" xlink:label="loc_us-gaap_RetirementPlanTypeDomain_30D29C21AE5A54C53C5C46F8C9388B3F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RetirementPlanTypeAxis_C9265E9D573AAFB8616046F8C9388E70" xlink:to="loc_us-gaap_RetirementPlanTypeDomain_30D29C21AE5A54C53C5C46F8C9388B3F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PensionPlansDefinedBenefitMember" xlink:label="loc_us-gaap_PensionPlansDefinedBenefitMember_0BD6B7150A6E6ED7B51946F8C938A841" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RetirementPlanTypeDomain_30D29C21AE5A54C53C5C46F8C9388B3F" xlink:to="loc_us-gaap_PensionPlansDefinedBenefitMember_0BD6B7150A6E6ED7B51946F8C938A841" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RetirementPlanFundingStatusAxis" xlink:label="loc_us-gaap_RetirementPlanFundingStatusAxis_4CB0744F65869AB69F8746F8C93942FF" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_7A04443CD311BDC9B61B46F8C937ABC5" xlink:to="loc_us-gaap_RetirementPlanFundingStatusAxis_4CB0744F65869AB69F8746F8C93942FF" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RetirementPlanFundingStatusDomain" xlink:label="loc_us-gaap_RetirementPlanFundingStatusDomain_1DA3F9953A8D28054E7246F8C9399F41_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RetirementPlanFundingStatusAxis_4CB0744F65869AB69F8746F8C93942FF" xlink:to="loc_us-gaap_RetirementPlanFundingStatusDomain_1DA3F9953A8D28054E7246F8C9399F41_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RetirementPlanFundingStatusDomain" xlink:label="loc_us-gaap_RetirementPlanFundingStatusDomain_1DA3F9953A8D28054E7246F8C9399F41" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RetirementPlanFundingStatusAxis_4CB0744F65869AB69F8746F8C93942FF" xlink:to="loc_us-gaap_RetirementPlanFundingStatusDomain_1DA3F9953A8D28054E7246F8C9399F41" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FundedPlanMember" xlink:label="loc_us-gaap_FundedPlanMember_3EA465FA67C3872508D646F8C9391DBA" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RetirementPlanFundingStatusDomain_1DA3F9953A8D28054E7246F8C9399F41" xlink:to="loc_us-gaap_FundedPlanMember_3EA465FA67C3872508D646F8C9391DBA" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DefinedBenefitPlanContributionsByEmployer" xlink:label="loc_us-gaap_DefinedBenefitPlanContributionsByEmployer_F856ACA1F09DE1A135D946F8C93ACD50" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_DCBCA4C03B1D036AB9DB46F8C93AF9E1" xlink:to="loc_us-gaap_DefinedBenefitPlanContributionsByEmployer_F856ACA1F09DE1A135D946F8C93ACD50" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossBeforeTax" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossBeforeTax_0E8EBE99B5717B23A1F146F8C93A4B5C" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_DCBCA4C03B1D036AB9DB46F8C93AF9E1" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossBeforeTax_0E8EBE99B5717B23A1F146F8C93A4B5C" xlink:type="arc" />
    <link:loc xlink:href="ucbi-20190930.xsd#ucbi_DefinedBenefitPlanPlanSettlementExpenseUponPlanTermination" xlink:label="loc_ucbi_DefinedBenefitPlanPlanSettlementExpenseUponPlanTermination_3E1B4A82C7708AD9C80046F8C93AD850" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_DCBCA4C03B1D036AB9DB46F8C93AF9E1" xlink:to="loc_ucbi_DefinedBenefitPlanPlanSettlementExpenseUponPlanTermination_3E1B4A82C7708AD9C80046F8C93AD850" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DefinedBenefitPlanRecognizedNetGainLossDueToSettlements1" xlink:label="loc_us-gaap_DefinedBenefitPlanRecognizedNetGainLossDueToSettlements1_293F1ED5C9F816DDACA746F94DEA4A64" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_DCBCA4C03B1D036AB9DB46F8C93AF9E1" xlink:to="loc_us-gaap_DefinedBenefitPlanRecognizedNetGainLossDueToSettlements1_293F1ED5C9F816DDACA746F94DEA4A64" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://ucbi.com/role/TerminationOfDefinedBenefitPlanNotes" xlink:type="extended" />
</link:linkbase>
