<?xml version="1.0" encoding="UTF-8"?>

<!--XBRL Document Created with the Workiva Platform-->
<!--Copyright 2026 Workiva-->
<!--r:019c76d5-35da-7af1-bab6-11e53f2d22d8,g:b9f5e4bb-b807-4437-89c3-21c518a42c3b-->
<link:linkbase xmlns:link="http://www.xbrl.org/2003/linkbase" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xbrldt="http://xbrl.org/2005/xbrldt" xsi:schemaLocation="http://www.xbrl.org/2003/linkbase http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd">
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/all" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#all"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#hypercube-dimension"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-default"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-domain"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#domain-member"/>
  <link:roleRef roleURI="http://www.mtb.com/role/DocumentandEntityInformation" xlink:type="simple" xlink:href="mtb-20260331.xsd#DocumentandEntityInformation"/>
  <link:definitionLink xlink:role="http://www.mtb.com/role/DocumentandEntityInformation" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentInformationLineItems_019c76d5-3c23-7f93-a216-6fb99764dc91" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_DocumentInformationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentInformationTable_019c76d5-3c23-705b-b1fb-be68d1ff35a6" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_DocumentInformationTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_dei_DocumentInformationLineItems_019c76d5-3c23-7f93-a216-6fb99764dc91" xlink:to="loc_dei_DocumentInformationTable_019c76d5-3c23-705b-b1fb-be68d1ff35a6" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_019c76d5-3c23-7e99-971b-c819b5d1c57f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_dei_DocumentInformationTable_019c76d5-3c23-705b-b1fb-be68d1ff35a6" xlink:to="loc_us-gaap_StatementClassOfStockAxis_019c76d5-3c23-7e99-971b-c819b5d1c57f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_019c76d5-3c23-7e99-971b-c819b5d1c57f_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_019c76d5-3c23-7e99-971b-c819b5d1c57f" xlink:to="loc_us-gaap_ClassOfStockDomain_019c76d5-3c23-7e99-971b-c819b5d1c57f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_019c76d5-3c23-726e-959a-219991fce16b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_019c76d5-3c23-7e99-971b-c819b5d1c57f" xlink:to="loc_us-gaap_ClassOfStockDomain_019c76d5-3c23-726e-959a-219991fce16b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockMember_019c76d5-3c23-7825-a4bf-31199198f4e2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommonStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_019c76d5-3c23-726e-959a-219991fce16b" xlink:to="loc_us-gaap_CommonStockMember_019c76d5-3c23-7825-a4bf-31199198f4e2" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SeriesHPreferredStockMember_019c76d5-3c23-7f78-b977-289d0d3ff6ff" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SeriesHPreferredStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_019c76d5-3c23-726e-959a-219991fce16b" xlink:to="loc_us-gaap_SeriesHPreferredStockMember_019c76d5-3c23-7f78-b977-289d0d3ff6ff" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_SeriesJPreferredStockMember_019c76d5-3c23-7965-ae62-542cf1a4f023" xlink:href="mtb-20260331.xsd#mtb_SeriesJPreferredStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_019c76d5-3c23-726e-959a-219991fce16b" xlink:to="loc_mtb_SeriesJPreferredStockMember_019c76d5-3c23-7965-ae62-542cf1a4f023" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_SeriesKPreferredStockMember_019d4986-5f89-7490-8b36-c45712dc4fb7" xlink:href="mtb-20260331.xsd#mtb_SeriesKPreferredStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_019c76d5-3c23-726e-959a-219991fce16b" xlink:to="loc_mtb_SeriesKPreferredStockMember_019d4986-5f89-7490-8b36-c45712dc4fb7" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentType_019c76d5-3c23-7bc1-8e67-d1496ecde871" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_DocumentType"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019c76d5-3c23-7f93-a216-6fb99764dc91" xlink:to="loc_dei_DocumentType_019c76d5-3c23-7bc1-8e67-d1496ecde871" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentQuarterlyReport_019c76d5-3c23-75fd-ab39-db6e9fb2c218" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_DocumentQuarterlyReport"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019c76d5-3c23-7f93-a216-6fb99764dc91" xlink:to="loc_dei_DocumentQuarterlyReport_019c76d5-3c23-75fd-ab39-db6e9fb2c218" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentPeriodEndDate_019c76d5-3c23-7da6-8dda-0314982cd01e" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_DocumentPeriodEndDate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019c76d5-3c23-7f93-a216-6fb99764dc91" xlink:to="loc_dei_DocumentPeriodEndDate_019c76d5-3c23-7da6-8dda-0314982cd01e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityFileNumber_019c76d5-3c23-7536-bd11-ebd766f1c689" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityFileNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019c76d5-3c23-7f93-a216-6fb99764dc91" xlink:to="loc_dei_EntityFileNumber_019c76d5-3c23-7536-bd11-ebd766f1c689" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityRegistrantName_019c76d5-3c23-7e30-9de8-ad3ed3e61a04" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityRegistrantName"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019c76d5-3c23-7f93-a216-6fb99764dc91" xlink:to="loc_dei_EntityRegistrantName_019c76d5-3c23-7e30-9de8-ad3ed3e61a04" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityIncorporationStateCountryCode_019c76d5-3c23-7cf1-a4a2-632daa80e5d7" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityIncorporationStateCountryCode"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019c76d5-3c23-7f93-a216-6fb99764dc91" xlink:to="loc_dei_EntityIncorporationStateCountryCode_019c76d5-3c23-7cf1-a4a2-632daa80e5d7" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityTaxIdentificationNumber_019c76d5-3c23-7f2b-bf4a-c9cb246c554b" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityTaxIdentificationNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019c76d5-3c23-7f93-a216-6fb99764dc91" xlink:to="loc_dei_EntityTaxIdentificationNumber_019c76d5-3c23-7f2b-bf4a-c9cb246c554b" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressAddressLine1_019c76d5-3c23-7a56-9c98-21dda22efd26" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityAddressAddressLine1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019c76d5-3c23-7f93-a216-6fb99764dc91" xlink:to="loc_dei_EntityAddressAddressLine1_019c76d5-3c23-7a56-9c98-21dda22efd26" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressCityOrTown_019c76d5-3c23-7d89-b4f1-82ca8c334111" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityAddressCityOrTown"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019c76d5-3c23-7f93-a216-6fb99764dc91" xlink:to="loc_dei_EntityAddressCityOrTown_019c76d5-3c23-7d89-b4f1-82ca8c334111" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressStateOrProvince_019c76d5-3c23-72b3-a164-812dd674504f" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityAddressStateOrProvince"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019c76d5-3c23-7f93-a216-6fb99764dc91" xlink:to="loc_dei_EntityAddressStateOrProvince_019c76d5-3c23-72b3-a164-812dd674504f" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressPostalZipCode_019c76d5-3c23-7772-b96b-d2801b574fdf" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityAddressPostalZipCode"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019c76d5-3c23-7f93-a216-6fb99764dc91" xlink:to="loc_dei_EntityAddressPostalZipCode_019c76d5-3c23-7772-b96b-d2801b574fdf" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_CityAreaCode_019c76d5-3c23-77d0-abe6-5cd16f1e8450" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_CityAreaCode"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019c76d5-3c23-7f93-a216-6fb99764dc91" xlink:to="loc_dei_CityAreaCode_019c76d5-3c23-77d0-abe6-5cd16f1e8450" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LocalPhoneNumber_019c76d5-3c23-7aa0-9b3d-cbe6c4a42e82" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_LocalPhoneNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019c76d5-3c23-7f93-a216-6fb99764dc91" xlink:to="loc_dei_LocalPhoneNumber_019c76d5-3c23-7aa0-9b3d-cbe6c4a42e82" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_Security12bTitle_019c76d5-3c23-7900-bbbf-739d9f8fbed5" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_Security12bTitle"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019c76d5-3c23-7f93-a216-6fb99764dc91" xlink:to="loc_dei_Security12bTitle_019c76d5-3c23-7900-bbbf-739d9f8fbed5" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_TradingSymbol_019c76d5-3c23-7238-b6f8-8e84cddf8e66" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_TradingSymbol"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019c76d5-3c23-7f93-a216-6fb99764dc91" xlink:to="loc_dei_TradingSymbol_019c76d5-3c23-7238-b6f8-8e84cddf8e66" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_SecurityExchangeName_019c76d5-3c23-7580-bae8-1c04a8f0d190" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_SecurityExchangeName"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019c76d5-3c23-7f93-a216-6fb99764dc91" xlink:to="loc_dei_SecurityExchangeName_019c76d5-3c23-7580-bae8-1c04a8f0d190" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityCurrentReportingStatus_019c76d5-3c23-7f50-a9bb-fe049023516b" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityCurrentReportingStatus"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019c76d5-3c23-7f93-a216-6fb99764dc91" xlink:to="loc_dei_EntityCurrentReportingStatus_019c76d5-3c23-7f50-a9bb-fe049023516b" xlink:type="arc" order="16"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityInteractiveDataCurrent_019c76d5-3c23-7a9e-a80f-6cd7c59810a3" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityInteractiveDataCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019c76d5-3c23-7f93-a216-6fb99764dc91" xlink:to="loc_dei_EntityInteractiveDataCurrent_019c76d5-3c23-7a9e-a80f-6cd7c59810a3" xlink:type="arc" order="17"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityFilerCategory_019c76d5-3c23-7641-aba2-9af0f5f93234" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityFilerCategory"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019c76d5-3c23-7f93-a216-6fb99764dc91" xlink:to="loc_dei_EntityFilerCategory_019c76d5-3c23-7641-aba2-9af0f5f93234" xlink:type="arc" order="18"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntitySmallBusiness_019c76d5-3c23-76ef-bece-92b7b447b986" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntitySmallBusiness"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019c76d5-3c23-7f93-a216-6fb99764dc91" xlink:to="loc_dei_EntitySmallBusiness_019c76d5-3c23-76ef-bece-92b7b447b986" xlink:type="arc" order="19"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityEmergingGrowthCompany_019c76d5-3c23-7437-abe6-b29edc757179" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityEmergingGrowthCompany"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019c76d5-3c23-7f93-a216-6fb99764dc91" xlink:to="loc_dei_EntityEmergingGrowthCompany_019c76d5-3c23-7437-abe6-b29edc757179" xlink:type="arc" order="20"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityShellCompany_019c76d5-3c23-7d39-af63-977a74149312" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityShellCompany"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019c76d5-3c23-7f93-a216-6fb99764dc91" xlink:to="loc_dei_EntityShellCompany_019c76d5-3c23-7d39-af63-977a74149312" xlink:type="arc" order="21"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityCommonStockSharesOutstanding_019c76d5-3c23-7be5-b126-93aeb00457c1" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityCommonStockSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019c76d5-3c23-7f93-a216-6fb99764dc91" xlink:to="loc_dei_EntityCommonStockSharesOutstanding_019c76d5-3c23-7be5-b126-93aeb00457c1" xlink:type="arc" order="22"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityCentralIndexKey_019c76d5-3c23-7157-9562-f06a3c0299c4" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityCentralIndexKey"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019c76d5-3c23-7f93-a216-6fb99764dc91" xlink:to="loc_dei_EntityCentralIndexKey_019c76d5-3c23-7157-9562-f06a3c0299c4" xlink:type="arc" order="23"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentFiscalYearFocus_019c76d5-3c23-7464-833e-41274b5f7377" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_DocumentFiscalYearFocus"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019c76d5-3c23-7f93-a216-6fb99764dc91" xlink:to="loc_dei_DocumentFiscalYearFocus_019c76d5-3c23-7464-833e-41274b5f7377" xlink:type="arc" order="24"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentFiscalPeriodFocus_019c76d5-3c23-7670-8d5a-c1034f5628c2" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_DocumentFiscalPeriodFocus"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019c76d5-3c23-7f93-a216-6fb99764dc91" xlink:to="loc_dei_DocumentFiscalPeriodFocus_019c76d5-3c23-7670-8d5a-c1034f5628c2" xlink:type="arc" order="25"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_AmendmentFlag_019c76d5-3c23-7cbb-be65-3887bdb880a7" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_AmendmentFlag"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019c76d5-3c23-7f93-a216-6fb99764dc91" xlink:to="loc_dei_AmendmentFlag_019c76d5-3c23-7cbb-be65-3887bdb880a7" xlink:type="arc" order="26"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_CurrentFiscalYearEndDate_019c76d5-3c23-7d27-8da5-a7bb4900cb7a" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_CurrentFiscalYearEndDate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019c76d5-3c23-7f93-a216-6fb99764dc91" xlink:to="loc_dei_CurrentFiscalYearEndDate_019c76d5-3c23-7d27-8da5-a7bb4900cb7a" xlink:type="arc" order="27"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentTransitionReport_019c76d5-3c23-7e33-8362-d8918fd20970" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_DocumentTransitionReport"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019c76d5-3c23-7f93-a216-6fb99764dc91" xlink:to="loc_dei_DocumentTransitionReport_019c76d5-3c23-7e33-8362-d8918fd20970" xlink:type="arc" order="28"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.mtb.com/role/ConsolidatedBalanceSheetUnauditedParenthetical" xlink:type="simple" xlink:href="mtb-20260331.xsd#ConsolidatedBalanceSheetUnauditedParenthetical"/>
  <link:definitionLink xlink:role="http://www.mtb.com/role/ConsolidatedBalanceSheetUnauditedParenthetical" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_019c76d5-3c23-7045-976c-7b15e1bb2631" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_019c76d5-3c23-718d-a119-634035193ada" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_019c76d5-3c23-7045-976c-7b15e1bb2631" xlink:to="loc_us-gaap_StatementTable_019c76d5-3c23-718d-a119-634035193ada" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesAxis_019c76d5-3c23-79bc-83c0-1af165c3d983" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ConsolidatedEntitiesAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_019c76d5-3c23-718d-a119-634035193ada" xlink:to="loc_srt_ConsolidatedEntitiesAxis_019c76d5-3c23-79bc-83c0-1af165c3d983" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_019c76d5-3c23-79bc-83c0-1af165c3d983_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidatedEntitiesAxis_019c76d5-3c23-79bc-83c0-1af165c3d983" xlink:to="loc_srt_ConsolidatedEntitiesDomain_019c76d5-3c23-79bc-83c0-1af165c3d983_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_019c76d5-3c23-7b07-8300-94f504f95f50" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidatedEntitiesAxis_019c76d5-3c23-79bc-83c0-1af165c3d983" xlink:to="loc_srt_ConsolidatedEntitiesDomain_019c76d5-3c23-7b07-8300-94f504f95f50" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableInterestEntityPrimaryBeneficiaryMember_019c76d5-3c23-7340-9154-36bf9fa593b7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_VariableInterestEntityPrimaryBeneficiaryMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidatedEntitiesDomain_019c76d5-3c23-7b07-8300-94f504f95f50" xlink:to="loc_us-gaap_VariableInterestEntityPrimaryBeneficiaryMember_019c76d5-3c23-7340-9154-36bf9fa593b7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_CounterpartyNameAxis_019c76d5-3c23-7c26-9a3e-544f5f2b8553" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_CounterpartyNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_019c76d5-3c23-718d-a119-634035193ada" xlink:to="loc_srt_CounterpartyNameAxis_019c76d5-3c23-7c26-9a3e-544f5f2b8553" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RepurchaseAgreementCounterpartyNameDomain_019c76d5-3c23-7c26-9a3e-544f5f2b8553_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RepurchaseAgreementCounterpartyNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_CounterpartyNameAxis_019c76d5-3c23-7c26-9a3e-544f5f2b8553" xlink:to="loc_srt_RepurchaseAgreementCounterpartyNameDomain_019c76d5-3c23-7c26-9a3e-544f5f2b8553_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RepurchaseAgreementCounterpartyNameDomain_019c76d5-3c23-7a19-a1dc-42a4fbcecaf2" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RepurchaseAgreementCounterpartyNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_CounterpartyNameAxis_019c76d5-3c23-7c26-9a3e-544f5f2b8553" xlink:to="loc_srt_RepurchaseAgreementCounterpartyNameDomain_019c76d5-3c23-7a19-a1dc-42a4fbcecaf2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_MTBankMember_019c76d5-3c23-7f59-9192-bc5dc156a1c8" xlink:href="mtb-20260331.xsd#mtb_MTBankMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RepurchaseAgreementCounterpartyNameDomain_019c76d5-3c23-7a19-a1dc-42a4fbcecaf2" xlink:to="loc_mtb_MTBankMember_019c76d5-3c23-7f59-9192-bc5dc156a1c8" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LegalEntityAxis_019c76d5-3c23-7c22-b32a-8ea742c719de" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_LegalEntityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_019c76d5-3c23-718d-a119-634035193ada" xlink:to="loc_dei_LegalEntityAxis_019c76d5-3c23-7c22-b32a-8ea742c719de" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019c76d5-3c23-7c22-b32a-8ea742c719de_default" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_019c76d5-3c23-7c22-b32a-8ea742c719de" xlink:to="loc_dei_EntityDomain_019c76d5-3c23-7c22-b32a-8ea742c719de_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019c76d5-3c23-74f9-8451-8b0a3cb9dc41" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_019c76d5-3c23-7c22-b32a-8ea742c719de" xlink:to="loc_dei_EntityDomain_019c76d5-3c23-74f9-8451-8b0a3cb9dc41" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_MAndTMember_019c76d5-3c23-769f-ad59-e792aec2ea5d" xlink:href="mtb-20260331.xsd#mtb_MAndTMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_019c76d5-3c23-74f9-8451-8b0a3cb9dc41" xlink:to="loc_mtb_MAndTMember_019c76d5-3c23-769f-ad59-e792aec2ea5d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis_019c76d5-3c23-7ce1-b257-dffe1ec17db6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019c76d5-3c23-7045-976c-7b15e1bb2631" xlink:to="loc_us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis_019c76d5-3c23-7ce1-b257-dffe1ec17db6" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HeldToMaturitySecuritiesFairValue_019c76d5-3c23-7e30-bd99-3ea2ffd81ec4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HeldToMaturitySecuritiesFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019c76d5-3c23-7045-976c-7b15e1bb2631" xlink:to="loc_us-gaap_HeldToMaturitySecuritiesFairValue_019c76d5-3c23-7e30-bd99-3ea2ffd81ec4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_EquityAndOtherSecuritiesAtCost_019c76d5-3c23-7421-bf05-647bd5786f8b" xlink:href="mtb-20260331.xsd#mtb_EquityAndOtherSecuritiesAtCost"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019c76d5-3c23-7045-976c-7b15e1bb2631" xlink:to="loc_mtb_EquityAndOtherSecuritiesAtCost_019c76d5-3c23-7421-bf05-647bd5786f8b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockParOrStatedValuePerShare_019c76d5-3c23-7e9a-9de6-615096a281ee" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommonStockParOrStatedValuePerShare"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019c76d5-3c23-7045-976c-7b15e1bb2631" xlink:to="loc_us-gaap_CommonStockParOrStatedValuePerShare_019c76d5-3c23-7e9a-9de6-615096a281ee" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesAuthorized_019c76d5-3c23-7cc5-bfd6-8cf50fd6407e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommonStockSharesAuthorized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019c76d5-3c23-7045-976c-7b15e1bb2631" xlink:to="loc_us-gaap_CommonStockSharesAuthorized_019c76d5-3c23-7cc5-bfd6-8cf50fd6407e" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesIssued_019c76d5-3c23-73e8-91b4-72a421c86000" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommonStockSharesIssued"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019c76d5-3c23-7045-976c-7b15e1bb2631" xlink:to="loc_us-gaap_CommonStockSharesIssued_019c76d5-3c23-73e8-91b4-72a421c86000" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockCommonShares_019c76d5-3c23-77fd-b816-908e0b78e338" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TreasuryStockCommonShares"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019c76d5-3c23-7045-976c-7b15e1bb2631" xlink:to="loc_us-gaap_TreasuryStockCommonShares_019c76d5-3c23-77fd-b816-908e0b78e338" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableAccruedInterestBeforeAllowanceForCreditLoss_019c76d5-3c23-7c63-87bf-7e099b201ed7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableAccruedInterestBeforeAllowanceForCreditLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019c76d5-3c23-7045-976c-7b15e1bb2631" xlink:to="loc_us-gaap_FinancingReceivableAccruedInterestBeforeAllowanceForCreditLoss_019c76d5-3c23-7c63-87bf-7e099b201ed7" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SecuredLongTermDebt_019c76d5-3c23-7bfe-bad6-5aa6e5297a67" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SecuredLongTermDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019c76d5-3c23-7045-976c-7b15e1bb2631" xlink:to="loc_us-gaap_SecuredLongTermDebt_019c76d5-3c23-7bfe-bad6-5aa6e5297a67" xlink:type="arc" order="8"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.mtb.com/role/ConsolidatedStatementofChangesinShareholdersEquity" xlink:type="simple" xlink:href="mtb-20260331.xsd#ConsolidatedStatementofChangesinShareholdersEquity"/>
  <link:definitionLink xlink:role="http://www.mtb.com/role/ConsolidatedStatementofChangesinShareholdersEquity" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_019c76d5-3cf9-7bdb-88a8-51cfeb9bd143" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_019c76d5-3cf9-75e1-92d4-b91edb2a9d0b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_019c76d5-3cf9-7bdb-88a8-51cfeb9bd143" xlink:to="loc_us-gaap_StatementTable_019c76d5-3cf9-75e1-92d4-b91edb2a9d0b" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_019c76d5-3cf9-7337-8167-5d54e14bae23" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_019c76d5-3cf9-75e1-92d4-b91edb2a9d0b" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_019c76d5-3cf9-7337-8167-5d54e14bae23" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_019c76d5-3cf9-7337-8167-5d54e14bae23_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_019c76d5-3cf9-7337-8167-5d54e14bae23" xlink:to="loc_us-gaap_EquityComponentDomain_019c76d5-3cf9-7337-8167-5d54e14bae23_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_019c76d5-3cf9-7b3f-a5fb-f266c09c6b17" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_019c76d5-3cf9-7337-8167-5d54e14bae23" xlink:to="loc_us-gaap_EquityComponentDomain_019c76d5-3cf9-7b3f-a5fb-f266c09c6b17" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PreferredStockMember_019c76d5-3cf9-7f11-87c2-b573f7a248f0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PreferredStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019c76d5-3cf9-7b3f-a5fb-f266c09c6b17" xlink:to="loc_us-gaap_PreferredStockMember_019c76d5-3cf9-7f11-87c2-b573f7a248f0" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockMember_019c76d5-3cf9-721a-aea0-0e6c09a0b81e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommonStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019c76d5-3cf9-7b3f-a5fb-f266c09c6b17" xlink:to="loc_us-gaap_CommonStockMember_019c76d5-3cf9-721a-aea0-0e6c09a0b81e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdditionalPaidInCapitalMember_019c76d5-3cf9-7119-a4a0-0df705fcb289" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AdditionalPaidInCapitalMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019c76d5-3cf9-7b3f-a5fb-f266c09c6b17" xlink:to="loc_us-gaap_AdditionalPaidInCapitalMember_019c76d5-3cf9-7119-a4a0-0df705fcb289" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetainedEarningsMember_019c76d5-3cf9-7e8b-8653-93513b01ae8a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RetainedEarningsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019c76d5-3cf9-7b3f-a5fb-f266c09c6b17" xlink:to="loc_us-gaap_RetainedEarningsMember_019c76d5-3cf9-7e8b-8653-93513b01ae8a" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_019c76d5-3cf9-7812-865c-059b3c05c8f0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019c76d5-3cf9-7b3f-a5fb-f266c09c6b17" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_019c76d5-3cf9-7812-865c-059b3c05c8f0" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockCommonMember_019c76d5-3cf9-7f6d-b47b-60b69f4e4fa9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TreasuryStockCommonMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019c76d5-3cf9-7b3f-a5fb-f266c09c6b17" xlink:to="loc_us-gaap_TreasuryStockCommonMember_019c76d5-3cf9-7f6d-b47b-60b69f4e4fa9" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_019c76d5-3cf9-7d0c-bf8a-ecece5b9e7ab" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_019c76d5-3cf9-75e1-92d4-b91edb2a9d0b" xlink:to="loc_us-gaap_StatementClassOfStockAxis_019c76d5-3cf9-7d0c-bf8a-ecece5b9e7ab" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_019c76d5-3cf9-7d0c-bf8a-ecece5b9e7ab_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_019c76d5-3cf9-7d0c-bf8a-ecece5b9e7ab" xlink:to="loc_us-gaap_ClassOfStockDomain_019c76d5-3cf9-7d0c-bf8a-ecece5b9e7ab_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_019c76d5-3cf9-72b4-8dee-73212f6d357e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_019c76d5-3cf9-7d0c-bf8a-ecece5b9e7ab" xlink:to="loc_us-gaap_ClassOfStockDomain_019c76d5-3cf9-72b4-8dee-73212f6d357e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SeriesEPreferredStockMember_019c76d5-3cf9-78f7-93ea-a702a3b637dd" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SeriesEPreferredStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_019c76d5-3cf9-72b4-8dee-73212f6d357e" xlink:to="loc_us-gaap_SeriesEPreferredStockMember_019c76d5-3cf9-78f7-93ea-a702a3b637dd" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_SeriesJPreferredStockMember_019c76d5-3cf9-779d-9b52-60f720e96976" xlink:href="mtb-20260331.xsd#mtb_SeriesJPreferredStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_019c76d5-3cf9-72b4-8dee-73212f6d357e" xlink:to="loc_mtb_SeriesJPreferredStockMember_019c76d5-3cf9-779d-9b52-60f720e96976" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019c76d5-3cf9-7943-a713-a6834114837b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncreaseDecreaseInStockholdersEquityRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019c76d5-3cf9-7bdb-88a8-51cfeb9bd143" xlink:to="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019c76d5-3cf9-7943-a713-a6834114837b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_019c76d5-3cf9-7669-a114-a19dad0cbbd5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockholdersEquity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019c76d5-3cf9-7943-a713-a6834114837b" xlink:to="loc_us-gaap_StockholdersEquity_019c76d5-3cf9-7669-a114-a19dad0cbbd5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_FairValueElectionResidentialMortgageLoanServicingRightAssets_019d4ea1-9cad-7c5d-87ce-df892109a2c4" xlink:href="mtb-20260331.xsd#mtb_FairValueElectionResidentialMortgageLoanServicingRightAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019c76d5-3cf9-7943-a713-a6834114837b" xlink:to="loc_mtb_FairValueElectionResidentialMortgageLoanServicingRightAssets_019d4ea1-9cad-7c5d-87ce-df892109a2c4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ComprehensiveIncomeNetOfTax_019c76d5-3cf9-718b-9113-22823c4180c2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ComprehensiveIncomeNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019c76d5-3cf9-7943-a713-a6834114837b" xlink:to="loc_us-gaap_ComprehensiveIncomeNetOfTax_019c76d5-3cf9-718b-9113-22823c4180c2" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockRedeemedOrCalledDuringPeriodValue_019d49a7-949b-7515-bac0-cd26961cbb10" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockRedeemedOrCalledDuringPeriodValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019c76d5-3cf9-7943-a713-a6834114837b" xlink:to="loc_us-gaap_StockRedeemedOrCalledDuringPeriodValue_019d49a7-949b-7515-bac0-cd26961cbb10" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DividendsPreferredStockCash_019c76d5-3cf9-7f9b-89c2-3f0a0a46e673" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DividendsPreferredStockCash"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019c76d5-3cf9-7943-a713-a6834114837b" xlink:to="loc_us-gaap_DividendsPreferredStockCash_019c76d5-3cf9-7f9b-89c2-3f0a0a46e673" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockValueAcquiredCostMethod_019c76d5-3cf9-7e84-9a64-d526313dc0e9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TreasuryStockValueAcquiredCostMethod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019c76d5-3cf9-7943-a713-a6834114837b" xlink:to="loc_us-gaap_TreasuryStockValueAcquiredCostMethod_019c76d5-3cf9-7e84-9a64-d526313dc0e9" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_ShareBasedCompensationExpenseNet_019c76d5-3cf9-769f-8d10-4c9bf7a6ade7" xlink:href="mtb-20260331.xsd#mtb_ShareBasedCompensationExpenseNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019c76d5-3cf9-7943-a713-a6834114837b" xlink:to="loc_mtb_ShareBasedCompensationExpenseNet_019c76d5-3cf9-769f-8d10-4c9bf7a6ade7" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DividendsCommonStockCash_019c76d5-3cf9-7aed-aa43-69331692d67b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DividendsCommonStockCash"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019c76d5-3cf9-7943-a713-a6834114837b" xlink:to="loc_us-gaap_DividendsCommonStockCash_019c76d5-3cf9-7aed-aa43-69331692d67b" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_019c76d5-3cf9-7ebe-83f0-1bb1638593a5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockholdersEquity"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockDividendsPerShareDeclared_019c76d5-3cf9-7058-b70c-5aa9df95966b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommonStockDividendsPerShareDeclared"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019c76d5-3cf9-7bdb-88a8-51cfeb9bd143" xlink:to="loc_us-gaap_CommonStockDividendsPerShareDeclared_019c76d5-3cf9-7058-b70c-5aa9df95966b" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.mtb.com/role/SignificantaccountingpoliciesAdditionalInformationDetails" xlink:type="simple" xlink:href="mtb-20260331.xsd#SignificantaccountingpoliciesAdditionalInformationDetails"/>
  <link:definitionLink xlink:role="http://www.mtb.com/role/SignificantaccountingpoliciesAdditionalInformationDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ServicingAssetsAtFairValueLineItems_019d4ea4-a284-7bf7-af02-7915d9fef112" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ServicingAssetsAtFairValueLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ServicingAssetsAtFairValueTable_019d4ea4-a284-7ee1-952e-a6aaab0e8de8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ServicingAssetsAtFairValueTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ServicingAssetsAtFairValueLineItems_019d4ea4-a284-7bf7-af02-7915d9fef112" xlink:to="loc_us-gaap_ServicingAssetsAtFairValueTable_019d4ea4-a284-7ee1-952e-a6aaab0e8de8" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentAxis_019d4ea4-a284-7f1f-8fc4-3d45d80c5a4d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancialInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ServicingAssetsAtFairValueTable_019d4ea4-a284-7ee1-952e-a6aaab0e8de8" xlink:to="loc_us-gaap_FinancialInstrumentAxis_019d4ea4-a284-7f1f-8fc4-3d45d80c5a4d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019d4ea4-a284-7f1f-8fc4-3d45d80c5a4d_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_019d4ea4-a284-7f1f-8fc4-3d45d80c5a4d" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019d4ea4-a284-7f1f-8fc4-3d45d80c5a4d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019d4ea4-a284-7ac5-8d37-115d900c60db" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_019d4ea4-a284-7f1f-8fc4-3d45d80c5a4d" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019d4ea4-a284-7ac5-8d37-115d900c60db" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ResidentialMortgageMember_019d4ea4-a284-74ec-af61-120a7c2e7c2f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ResidentialMortgageMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019d4ea4-a284-7ac5-8d37-115d900c60db" xlink:to="loc_us-gaap_ResidentialMortgageMember_019d4ea4-a284-74ec-af61-120a7c2e7c2f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetAtFairValueChangesInFairValueResultingFromChangesInAssumptions_019d4ea4-a284-721d-a814-59febc7b48a7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AssetAtFairValueChangesInFairValueResultingFromChangesInAssumptions"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ServicingAssetsAtFairValueLineItems_019d4ea4-a284-7bf7-af02-7915d9fef112" xlink:to="loc_us-gaap_AssetAtFairValueChangesInFairValueResultingFromChangesInAssumptions_019d4ea4-a284-721d-a814-59febc7b48a7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_ServicingAssetAtFairValuePeriodIncreaseDecreaseNetOfTax_019d4ea4-a284-7f90-b5ec-ca35ff5b3229" xlink:href="mtb-20260331.xsd#mtb_ServicingAssetAtFairValuePeriodIncreaseDecreaseNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ServicingAssetsAtFairValueLineItems_019d4ea4-a284-7bf7-af02-7915d9fef112" xlink:to="loc_mtb_ServicingAssetAtFairValuePeriodIncreaseDecreaseNetOfTax_019d4ea4-a284-7f90-b5ec-ca35ff5b3229" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.mtb.com/role/SignificantaccountingpoliciesScheduleofPriorPeriodAdjustmentsDetails" xlink:type="simple" xlink:href="mtb-20260331.xsd#SignificantaccountingpoliciesScheduleofPriorPeriodAdjustmentsDetails"/>
  <link:definitionLink xlink:role="http://www.mtb.com/role/SignificantaccountingpoliciesScheduleofPriorPeriodAdjustmentsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReclassificationLineItems_019d4e8d-d829-7100-9702-ee9c0a46795b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ReclassificationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReclassificationTable_019d4e8d-d829-7b00-8be4-977f52ead18e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ReclassificationTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ReclassificationLineItems_019d4e8d-d829-7100-9702-ee9c0a46795b" xlink:to="loc_us-gaap_ReclassificationTable_019d4e8d-d829-7b00-8be4-977f52ead18e" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RestatementAxis_019d4e8d-d829-7621-b798-4e74258fb7f8" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RestatementAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ReclassificationTable_019d4e8d-d829-7b00-8be4-977f52ead18e" xlink:to="loc_srt_RestatementAxis_019d4e8d-d829-7621-b798-4e74258fb7f8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RestatementDomain_019d4e8d-d829-7621-b798-4e74258fb7f8_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RestatementDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RestatementAxis_019d4e8d-d829-7621-b798-4e74258fb7f8" xlink:to="loc_srt_RestatementDomain_019d4e8d-d829-7621-b798-4e74258fb7f8_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RestatementDomain_019d4e8d-d829-7b08-a834-13f6000c5760" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RestatementDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RestatementAxis_019d4e8d-d829-7621-b798-4e74258fb7f8" xlink:to="loc_srt_RestatementDomain_019d4e8d-d829-7b08-a834-13f6000c5760" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScenarioPreviouslyReportedMember_019d4e8d-d829-75f0-96eb-3ac1ea474805" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ScenarioPreviouslyReportedMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RestatementDomain_019d4e8d-d829-7b08-a834-13f6000c5760" xlink:to="loc_srt_ScenarioPreviouslyReportedMember_019d4e8d-d829-75f0-96eb-3ac1ea474805" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromPaymentsForInInterestBearingDepositsInBanks_019d4e8d-d829-7a86-97a8-c92bc58dfe77" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ProceedsFromPaymentsForInInterestBearingDepositsInBanks"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ReclassificationLineItems_019d4e8d-d829-7100-9702-ee9c0a46795b" xlink:to="loc_us-gaap_ProceedsFromPaymentsForInInterestBearingDepositsInBanks_019d4e8d-d829-7a86-97a8-c92bc58dfe77" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInInvestingActivities_019d4e8d-d829-72e7-a9e4-e72f0d09645a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NetCashProvidedByUsedInInvestingActivities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ReclassificationLineItems_019d4e8d-d829-7100-9702-ee9c0a46795b" xlink:to="loc_us-gaap_NetCashProvidedByUsedInInvestingActivities_019d4e8d-d829-72e7-a9e4-e72f0d09645a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseExcludingExchangeRateEffect_019d4e8d-d829-7181-b316-2ee63eed3ad5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseExcludingExchangeRateEffect"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ReclassificationLineItems_019d4e8d-d829-7100-9702-ee9c0a46795b" xlink:to="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseExcludingExchangeRateEffect_019d4e8d-d829-7181-b316-2ee63eed3ad5" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_019d4e8d-d829-73d4-be90-2cdfa4c2764a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ReclassificationLineItems_019d4e8d-d829-7100-9702-ee9c0a46795b" xlink:to="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_019d4e8d-d829-73d4-be90-2cdfa4c2764a" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_019d4e8e-7e6e-7720-9d96-138e2d27410e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.mtb.com/role/InvestmentsecuritiesAmortizedCostandEstimatedFairValueofInvestmentSecuritiesDetail" xlink:type="simple" xlink:href="mtb-20260331.xsd#InvestmentsecuritiesAmortizedCostandEstimatedFairValueofInvestmentSecuritiesDetail"/>
  <link:definitionLink xlink:role="http://www.mtb.com/role/InvestmentsecuritiesAmortizedCostandEstimatedFairValueofInvestmentSecuritiesDetail" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_019c76d5-3cf9-7c07-8f0a-757d5d53e3fa" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleTable_019c76d5-3cf9-782a-a446-e57f00cbc716" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtSecuritiesAvailableForSaleTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_019c76d5-3cf9-7c07-8f0a-757d5d53e3fa" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleTable_019c76d5-3cf9-782a-a446-e57f00cbc716" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentAxis_019c76d5-3cf9-7d75-84f3-922906c7f91a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancialInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtSecuritiesAvailableForSaleTable_019c76d5-3cf9-782a-a446-e57f00cbc716" xlink:to="loc_us-gaap_FinancialInstrumentAxis_019c76d5-3cf9-7d75-84f3-922906c7f91a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019c76d5-3cf9-7d75-84f3-922906c7f91a_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_019c76d5-3cf9-7d75-84f3-922906c7f91a" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019c76d5-3cf9-7d75-84f3-922906c7f91a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019c76d5-3cf9-7b28-9cd5-4a3fec3425b3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_019c76d5-3cf9-7d75-84f3-922906c7f91a" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019c76d5-3cf9-7b28-9cd5-4a3fec3425b3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_USTreasuryAndGovernmentMember_019c76d5-3cf9-7cb0-8f51-5ef6708b8a4b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_USTreasuryAndGovernmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019c76d5-3cf9-7b28-9cd5-4a3fec3425b3" xlink:to="loc_us-gaap_USTreasuryAndGovernmentMember_019c76d5-3cf9-7cb0-8f51-5ef6708b8a4b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommercialMortgageBackedSecuritiesMember_019c76d5-3cf9-768f-b649-cf2bac3e9d4d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommercialMortgageBackedSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019c76d5-3cf9-7b28-9cd5-4a3fec3425b3" xlink:to="loc_us-gaap_CommercialMortgageBackedSecuritiesMember_019c76d5-3cf9-768f-b649-cf2bac3e9d4d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ResidentialMortgageBackedSecuritiesMember_019c76d5-3cf9-7a5f-8664-bc68854b3cef" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ResidentialMortgageBackedSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019c76d5-3cf9-7b28-9cd5-4a3fec3425b3" xlink:to="loc_us-gaap_ResidentialMortgageBackedSecuritiesMember_019c76d5-3cf9-7a5f-8664-bc68854b3cef" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MortgageBackedSecuritiesIssuedByPrivateEnterprisesMember_019c76d5-3cf9-734d-ab62-dc229384ec53" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_MortgageBackedSecuritiesIssuedByPrivateEnterprisesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019c76d5-3cf9-7b28-9cd5-4a3fec3425b3" xlink:to="loc_us-gaap_MortgageBackedSecuritiesIssuedByPrivateEnterprisesMember_019c76d5-3cf9-734d-ab62-dc229384ec53" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_USStatesAndPoliticalSubdivisionsMember_019c76d5-3cf9-7992-bfea-0705566a3c3f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_USStatesAndPoliticalSubdivisionsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019c76d5-3cf9-7b28-9cd5-4a3fec3425b3" xlink:to="loc_us-gaap_USStatesAndPoliticalSubdivisionsMember_019c76d5-3cf9-7992-bfea-0705566a3c3f" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherDebtSecuritiesMember_019c76d5-3cf9-71b1-8112-19b98d253a71" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherDebtSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019c76d5-3cf9-7b28-9cd5-4a3fec3425b3" xlink:to="loc_us-gaap_OtherDebtSecuritiesMember_019c76d5-3cf9-71b1-8112-19b98d253a71" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesMember_019c76d5-3cf9-7371-8dbd-26c788d8b9d1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019c76d5-3cf9-7b28-9cd5-4a3fec3425b3" xlink:to="loc_us-gaap_DebtSecuritiesMember_019c76d5-3cf9-7371-8dbd-26c788d8b9d1" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis_019c76d5-3cf9-7346-8ef8-6566cb4dec21" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_019c76d5-3cf9-7c07-8f0a-757d5d53e3fa" xlink:to="loc_us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis_019c76d5-3cf9-7346-8ef8-6566cb4dec21" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax_019c76d5-3cf9-7ac8-80cf-1549af0caa34" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_019c76d5-3cf9-7c07-8f0a-757d5d53e3fa" xlink:to="loc_us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax_019c76d5-3cf9-7ac8-80cf-1549af0caa34" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax_019c76d5-3cf9-77cd-aeaf-55eb7584f566" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_019c76d5-3cf9-7c07-8f0a-757d5d53e3fa" xlink:to="loc_us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax_019c76d5-3cf9-77cd-aeaf-55eb7584f566" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtSecurities_019c76d5-3cf9-79d7-bb0e-ce407520b963" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AvailableForSaleSecuritiesDebtSecurities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_019c76d5-3cf9-7c07-8f0a-757d5d53e3fa" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtSecurities_019c76d5-3cf9-79d7-bb0e-ce407520b963" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_InvestmentInDebtSecuritiesAmortizedCost_019c76d5-3cf9-7d83-a76d-44b1dec1cbd5" xlink:href="mtb-20260331.xsd#mtb_InvestmentInDebtSecuritiesAmortizedCost"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_019c76d5-3cf9-7c07-8f0a-757d5d53e3fa" xlink:to="loc_mtb_InvestmentInDebtSecuritiesAmortizedCost_019c76d5-3cf9-7d83-a76d-44b1dec1cbd5" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_InvestmentInDebtSecuritiesGrossUnrealizedGains_019c76d5-3cf9-7a36-8b73-641a585e47cc" xlink:href="mtb-20260331.xsd#mtb_InvestmentInDebtSecuritiesGrossUnrealizedGains"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_019c76d5-3cf9-7c07-8f0a-757d5d53e3fa" xlink:to="loc_mtb_InvestmentInDebtSecuritiesGrossUnrealizedGains_019c76d5-3cf9-7a36-8b73-641a585e47cc" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_InvestmentInDebtSecuritiesGrossUnrealizedLosses_019c76d5-3cf9-7e78-a3c7-fb53d37111d2" xlink:href="mtb-20260331.xsd#mtb_InvestmentInDebtSecuritiesGrossUnrealizedLosses"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_019c76d5-3cf9-7c07-8f0a-757d5d53e3fa" xlink:to="loc_mtb_InvestmentInDebtSecuritiesGrossUnrealizedLosses_019c76d5-3cf9-7e78-a3c7-fb53d37111d2" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_InvestmentInDebtSecuritiesEstimatedFairValue_019c76d5-3cf9-7f7a-94db-0dfcab6583be" xlink:href="mtb-20260331.xsd#mtb_InvestmentInDebtSecuritiesEstimatedFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_019c76d5-3cf9-7c07-8f0a-757d5d53e3fa" xlink:to="loc_mtb_InvestmentInDebtSecuritiesEstimatedFairValue_019c76d5-3cf9-7f7a-94db-0dfcab6583be" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_ReadilyMarketableSecuritiesAtFairValueAmortizedCost_019c76d5-3cf9-7dee-a87b-3b373d2e47a0" xlink:href="mtb-20260331.xsd#mtb_ReadilyMarketableSecuritiesAtFairValueAmortizedCost"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_019c76d5-3cf9-7c07-8f0a-757d5d53e3fa" xlink:to="loc_mtb_ReadilyMarketableSecuritiesAtFairValueAmortizedCost_019c76d5-3cf9-7dee-a87b-3b373d2e47a0" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_ReadilyMarketableSecuritiesAtFairValueGrossUnrealizedGains_019c76d5-3cf9-7e70-aeb8-d93229cadf8b" xlink:href="mtb-20260331.xsd#mtb_ReadilyMarketableSecuritiesAtFairValueGrossUnrealizedGains"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_019c76d5-3cf9-7c07-8f0a-757d5d53e3fa" xlink:to="loc_mtb_ReadilyMarketableSecuritiesAtFairValueGrossUnrealizedGains_019c76d5-3cf9-7e70-aeb8-d93229cadf8b" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_ReadilyMarketableSecuritiesAtFairValueGrossUnrealizedLosses_019c76d5-3cf9-7cc9-b956-3e427ffea640" xlink:href="mtb-20260331.xsd#mtb_ReadilyMarketableSecuritiesAtFairValueGrossUnrealizedLosses"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_019c76d5-3cf9-7c07-8f0a-757d5d53e3fa" xlink:to="loc_mtb_ReadilyMarketableSecuritiesAtFairValueGrossUnrealizedLosses_019c76d5-3cf9-7cc9-b956-3e427ffea640" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_ReadilyMarketableSecuritiesAtEstimatedFairValue_019c76d5-3cf9-7f34-9301-06b10dd57325" xlink:href="mtb-20260331.xsd#mtb_ReadilyMarketableSecuritiesAtEstimatedFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_019c76d5-3cf9-7c07-8f0a-757d5d53e3fa" xlink:to="loc_mtb_ReadilyMarketableSecuritiesAtEstimatedFairValue_019c76d5-3cf9-7f34-9301-06b10dd57325" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherInvestmentsAndSecuritiesAtCost_019c76d5-3cf9-710b-8306-8747614bdba7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherInvestmentsAndSecuritiesAtCost"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_019c76d5-3cf9-7c07-8f0a-757d5d53e3fa" xlink:to="loc_us-gaap_OtherInvestmentsAndSecuritiesAtCost_019c76d5-3cf9-710b-8306-8747614bdba7" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FederalHomeLoanBankStockAndFederalReserveBankStock_019c76d5-3cf9-7b72-93b7-ac142f538a1b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FederalHomeLoanBankStockAndFederalReserveBankStock"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_019c76d5-3cf9-7c07-8f0a-757d5d53e3fa" xlink:to="loc_us-gaap_FederalHomeLoanBankStockAndFederalReserveBankStock_019c76d5-3cf9-7b72-93b7-ac142f538a1b" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_EquityAndOtherSecuritiesAtCost_019c76d5-3cf9-782e-a131-73e613da5006" xlink:href="mtb-20260331.xsd#mtb_EquityAndOtherSecuritiesAtCost"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_019c76d5-3cf9-7c07-8f0a-757d5d53e3fa" xlink:to="loc_mtb_EquityAndOtherSecuritiesAtCost_019c76d5-3cf9-782e-a131-73e613da5006" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_EquitySecuritiesGrossUnrealizedGains_019c76d5-3cf9-7722-a691-e0dcce24c154" xlink:href="mtb-20260331.xsd#mtb_EquitySecuritiesGrossUnrealizedGains"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_019c76d5-3cf9-7c07-8f0a-757d5d53e3fa" xlink:to="loc_mtb_EquitySecuritiesGrossUnrealizedGains_019c76d5-3cf9-7722-a691-e0dcce24c154" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_EquitySecuritiesGrossUnrealizedLosses_019c76d5-3cf9-7fb4-82f0-070f21488bd6" xlink:href="mtb-20260331.xsd#mtb_EquitySecuritiesGrossUnrealizedLosses"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_019c76d5-3cf9-7c07-8f0a-757d5d53e3fa" xlink:to="loc_mtb_EquitySecuritiesGrossUnrealizedLosses_019c76d5-3cf9-7fb4-82f0-070f21488bd6" xlink:type="arc" order="16"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_EquityAndOtherSecuritiesEstimatedFairValue_019c76d5-3cf9-7061-a872-8b3efdf949ed" xlink:href="mtb-20260331.xsd#mtb_EquityAndOtherSecuritiesEstimatedFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_019c76d5-3cf9-7c07-8f0a-757d5d53e3fa" xlink:to="loc_mtb_EquityAndOtherSecuritiesEstimatedFairValue_019c76d5-3cf9-7061-a872-8b3efdf949ed" xlink:type="arc" order="17"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestReceivableAndOtherAssets_019c76d5-3cf9-7d00-a959-781dfeac731f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InterestReceivableAndOtherAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_019c76d5-3cf9-7c07-8f0a-757d5d53e3fa" xlink:to="loc_us-gaap_InterestReceivableAndOtherAssets_019c76d5-3cf9-7d00-a959-781dfeac731f" xlink:type="arc" order="18"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfHeldToMaturitySecuritiesLineItems_019c76d5-3cf9-79a5-a5a7-74b26ba1c778" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfHeldToMaturitySecuritiesLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfHeldToMaturitySecuritiesTable_019c76d5-3cf9-7696-a264-4b6e99afb1ea" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfHeldToMaturitySecuritiesTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ScheduleOfHeldToMaturitySecuritiesLineItems_019c76d5-3cf9-79a5-a5a7-74b26ba1c778" xlink:to="loc_us-gaap_ScheduleOfHeldToMaturitySecuritiesTable_019c76d5-3cf9-7696-a264-4b6e99afb1ea" xlink:type="arc" order="2" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentAxis_019c76d5-3cf9-743c-a6bd-80900a77d4ff" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancialInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfHeldToMaturitySecuritiesTable_019c76d5-3cf9-7696-a264-4b6e99afb1ea" xlink:to="loc_us-gaap_FinancialInstrumentAxis_019c76d5-3cf9-743c-a6bd-80900a77d4ff" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019c76d5-3cf9-743c-a6bd-80900a77d4ff_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019c76d5-3cf9-7a68-ad06-2712c21db7b5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_USTreasuryAndGovernmentMember_019c76d5-3cf9-7c2e-b4a9-2a34f7d77659" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_USTreasuryAndGovernmentMember"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommercialMortgageBackedSecuritiesMember_019c76d5-3cf9-78a4-97b6-762fdd463071" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommercialMortgageBackedSecuritiesMember"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ResidentialMortgageBackedSecuritiesMember_019c76d5-3cf9-7d32-8718-19345d71dbac" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ResidentialMortgageBackedSecuritiesMember"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MortgageBackedSecuritiesIssuedByPrivateEnterprisesMember_019c76d5-3cf9-7531-9e35-76656dfffb21" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_MortgageBackedSecuritiesIssuedByPrivateEnterprisesMember"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_USStatesAndPoliticalSubdivisionsMember_019c76d5-3cf9-756d-9b73-be24290a9796" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_USStatesAndPoliticalSubdivisionsMember"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherDebtSecuritiesMember_019c76d5-3cf9-78ac-865d-550506fbd35a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherDebtSecuritiesMember"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HeldToMaturitySecuritiesClassifiedAbstract_019c76d5-3cf9-7708-9de6-ec06c37c1793" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HeldToMaturitySecuritiesClassifiedAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfHeldToMaturitySecuritiesLineItems_019c76d5-3cf9-79a5-a5a7-74b26ba1c778" xlink:to="loc_us-gaap_HeldToMaturitySecuritiesClassifiedAbstract_019c76d5-3cf9-7708-9de6-ec06c37c1793" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HeldToMaturitySecurities_019c76d5-3cf9-7575-8d57-8c8eb32cf9f3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HeldToMaturitySecurities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HeldToMaturitySecuritiesClassifiedAbstract_019c76d5-3cf9-7708-9de6-ec06c37c1793" xlink:to="loc_us-gaap_HeldToMaturitySecurities_019c76d5-3cf9-7575-8d57-8c8eb32cf9f3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingGain_019c76d5-3cf9-7293-a16f-1190d1ec7939" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingGain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HeldToMaturitySecuritiesClassifiedAbstract_019c76d5-3cf9-7708-9de6-ec06c37c1793" xlink:to="loc_us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingGain_019c76d5-3cf9-7293-a16f-1190d1ec7939" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingLoss_019c76d5-3cf9-7675-96f8-9586c0e7d432" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HeldToMaturitySecuritiesClassifiedAbstract_019c76d5-3cf9-7708-9de6-ec06c37c1793" xlink:to="loc_us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingLoss_019c76d5-3cf9-7675-96f8-9586c0e7d432" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HeldToMaturitySecuritiesFairValue_019c76d5-3cfa-75ec-b5ad-7ea2bed00df1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HeldToMaturitySecuritiesFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HeldToMaturitySecuritiesClassifiedAbstract_019c76d5-3cf9-7708-9de6-ec06c37c1793" xlink:to="loc_us-gaap_HeldToMaturitySecuritiesFairValue_019c76d5-3cfa-75ec-b5ad-7ea2bed00df1" xlink:type="arc" order="4"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.mtb.com/role/InvestmentsecuritiesInvestmentSecuritiesinContinuousUnrealizedLossPositionDetail" xlink:type="simple" xlink:href="mtb-20260331.xsd#InvestmentsecuritiesInvestmentSecuritiesinContinuousUnrealizedLossPositionDetail"/>
  <link:definitionLink xlink:role="http://www.mtb.com/role/InvestmentsecuritiesInvestmentSecuritiesinContinuousUnrealizedLossPositionDetail" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_019c76d5-3cfa-7b24-835e-704ebe8f4b92" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleTable_019c76d5-3cfa-714a-9d98-8dc2797581e1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtSecuritiesAvailableForSaleTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_019c76d5-3cfa-7b24-835e-704ebe8f4b92" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleTable_019c76d5-3cfa-714a-9d98-8dc2797581e1" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentAxis_019c76d5-3cfa-7c17-94cf-badf1834fe62" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancialInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtSecuritiesAvailableForSaleTable_019c76d5-3cfa-714a-9d98-8dc2797581e1" xlink:to="loc_us-gaap_FinancialInstrumentAxis_019c76d5-3cfa-7c17-94cf-badf1834fe62" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019c76d5-3cfa-7c17-94cf-badf1834fe62_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_019c76d5-3cfa-7c17-94cf-badf1834fe62" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019c76d5-3cfa-7c17-94cf-badf1834fe62_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019c76d5-3cfa-7f9e-b079-45604e897bc1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_019c76d5-3cfa-7c17-94cf-badf1834fe62" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019c76d5-3cfa-7f9e-b079-45604e897bc1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_USTreasuryAndGovernmentMember_019c76d5-3cfa-743d-9c6a-5a909a1892ee" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_USTreasuryAndGovernmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019c76d5-3cfa-7f9e-b079-45604e897bc1" xlink:to="loc_us-gaap_USTreasuryAndGovernmentMember_019c76d5-3cfa-743d-9c6a-5a909a1892ee" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommercialMortgageBackedSecuritiesMember_019c76d5-3cfa-7182-ac17-f35de0c1a114" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommercialMortgageBackedSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019c76d5-3cfa-7f9e-b079-45604e897bc1" xlink:to="loc_us-gaap_CommercialMortgageBackedSecuritiesMember_019c76d5-3cfa-7182-ac17-f35de0c1a114" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ResidentialMortgageBackedSecuritiesMember_019c76d5-3cfa-739e-876b-96650c9c390b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ResidentialMortgageBackedSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019c76d5-3cfa-7f9e-b079-45604e897bc1" xlink:to="loc_us-gaap_ResidentialMortgageBackedSecuritiesMember_019c76d5-3cfa-739e-876b-96650c9c390b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherDebtSecuritiesMember_019c76d5-3cfa-71a9-a8f0-a917146942d0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherDebtSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019c76d5-3cfa-7f9e-b079-45604e897bc1" xlink:to="loc_us-gaap_OtherDebtSecuritiesMember_019c76d5-3cfa-71a9-a8f0-a917146942d0" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_USStatesAndPoliticalSubdivisionsMember_019c76d5-3cfa-7b52-856a-de5d63c12dc1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_USStatesAndPoliticalSubdivisionsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019c76d5-3cfa-7f9e-b079-45604e897bc1" xlink:to="loc_us-gaap_USStatesAndPoliticalSubdivisionsMember_019c76d5-3cfa-7b52-856a-de5d63c12dc1" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MortgageBackedSecuritiesIssuedByPrivateEnterprisesMember_019c76d5-3cfa-7aff-80b9-883a8577aeff" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_MortgageBackedSecuritiesIssuedByPrivateEnterprisesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019c76d5-3cfa-7f9e-b079-45604e897bc1" xlink:to="loc_us-gaap_MortgageBackedSecuritiesIssuedByPrivateEnterprisesMember_019c76d5-3cfa-7aff-80b9-883a8577aeff" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionAccumulatedLossAbstract_019c76d5-3cfa-72c8-8056-75aacb077a1a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionAccumulatedLossAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_019c76d5-3cfa-7b24-835e-704ebe8f4b92" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionAccumulatedLossAbstract_019c76d5-3cfa-72c8-8056-75aacb077a1a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12Months_019c76d5-3cfa-7842-a40c-c8526f8dbfb0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12Months"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionAccumulatedLossAbstract_019c76d5-3cfa-72c8-8056-75aacb077a1a" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12Months_019c76d5-3cfa-7842-a40c-c8526f8dbfb0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss_019c76d5-3cfa-7243-97c1-2373563fb53b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionAccumulatedLossAbstract_019c76d5-3cfa-72c8-8056-75aacb077a1a" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss_019c76d5-3cfa-7243-97c1-2373563fb53b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLonger_019c76d5-3cfa-764f-8f4f-1ef696dc29c3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLonger"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionAccumulatedLossAbstract_019c76d5-3cfa-72c8-8056-75aacb077a1a" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLonger_019c76d5-3cfa-764f-8f4f-1ef696dc29c3" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss_019c76d5-3cfa-7261-b16f-af38e904f8a2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionAccumulatedLossAbstract_019c76d5-3cfa-72c8-8056-75aacb077a1a" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss_019c76d5-3cfa-7261-b16f-af38e904f8a2" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleUnrealizedLossPosition_019de4d1-7ec8-7f97-a275-e42fb9683adf" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtSecuritiesAvailableForSaleUnrealizedLossPosition"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionAccumulatedLossAbstract_019c76d5-3cfa-72c8-8056-75aacb077a1a" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleUnrealizedLossPosition_019de4d1-7ec8-7f97-a275-e42fb9683adf" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleUnrealizedLossPositionAccumulatedLoss_019de4d9-65db-7a3b-adf2-44eab266aeeb" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtSecuritiesAvailableForSaleUnrealizedLossPositionAccumulatedLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionAccumulatedLossAbstract_019c76d5-3cfa-72c8-8056-75aacb077a1a" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleUnrealizedLossPositionAccumulatedLoss_019de4d9-65db-7a3b-adf2-44eab266aeeb" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_InvestmentSecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue_019c76d5-3cfa-7bec-8417-1bfec95ff439" xlink:href="mtb-20260331.xsd#mtb_InvestmentSecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_019c76d5-3cfa-7b24-835e-704ebe8f4b92" xlink:to="loc_mtb_InvestmentSecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue_019c76d5-3cfa-7bec-8417-1bfec95ff439" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_InvestmentSecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsAggregateLosses_019c76d5-3cfa-78a3-9168-473a8001e898" xlink:href="mtb-20260331.xsd#mtb_InvestmentSecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsAggregateLosses"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_019c76d5-3cfa-7b24-835e-704ebe8f4b92" xlink:to="loc_mtb_InvestmentSecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsAggregateLosses_019c76d5-3cfa-78a3-9168-473a8001e898" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_InvestmentSecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue_019c76d5-3cfa-7bda-8ff7-afa74a27256e" xlink:href="mtb-20260331.xsd#mtb_InvestmentSecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_019c76d5-3cfa-7b24-835e-704ebe8f4b92" xlink:to="loc_mtb_InvestmentSecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue_019c76d5-3cfa-7bda-8ff7-afa74a27256e" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_InvestmentSecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerAggregateLosses_019c76d5-3cfa-7d86-bb5d-682ebb7a0ba5" xlink:href="mtb-20260331.xsd#mtb_InvestmentSecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerAggregateLosses"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_019c76d5-3cfa-7b24-835e-704ebe8f4b92" xlink:to="loc_mtb_InvestmentSecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerAggregateLosses_019c76d5-3cfa-7d86-bb5d-682ebb7a0ba5" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_InvestmentSecuritiesContinuousUnrealizedLossPosition_019de529-7a24-7bc3-a7bc-558dd5533c31" xlink:href="mtb-20260331.xsd#mtb_InvestmentSecuritiesContinuousUnrealizedLossPosition"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_019c76d5-3cfa-7b24-835e-704ebe8f4b92" xlink:to="loc_mtb_InvestmentSecuritiesContinuousUnrealizedLossPosition_019de529-7a24-7bc3-a7bc-558dd5533c31" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_InvestmentSecuritiesContinuousUnrealizedLossPositionAggregateLosses_019de529-e1fa-7cb8-9822-3954d63eaa0e" xlink:href="mtb-20260331.xsd#mtb_InvestmentSecuritiesContinuousUnrealizedLossPositionAggregateLosses"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_019c76d5-3cfa-7b24-835e-704ebe8f4b92" xlink:to="loc_mtb_InvestmentSecuritiesContinuousUnrealizedLossPositionAggregateLosses_019de529-e1fa-7cb8-9822-3954d63eaa0e" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfHeldToMaturitySecuritiesLineItems_019c76d5-3cfa-7711-b300-92614709fa6e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfHeldToMaturitySecuritiesLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfHeldToMaturitySecuritiesTable_019c76d5-3cfa-73b1-b29a-114a9cd1b713" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfHeldToMaturitySecuritiesTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ScheduleOfHeldToMaturitySecuritiesLineItems_019c76d5-3cfa-7711-b300-92614709fa6e" xlink:to="loc_us-gaap_ScheduleOfHeldToMaturitySecuritiesTable_019c76d5-3cfa-73b1-b29a-114a9cd1b713" xlink:type="arc" order="2" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentAxis_019c76d5-3cfa-7761-a6da-2fc0c9dfedb7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancialInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfHeldToMaturitySecuritiesTable_019c76d5-3cfa-73b1-b29a-114a9cd1b713" xlink:to="loc_us-gaap_FinancialInstrumentAxis_019c76d5-3cfa-7761-a6da-2fc0c9dfedb7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019c76d5-3cfa-7761-a6da-2fc0c9dfedb7_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019c76d5-3cfa-7e09-9dc1-6cc91f4f9b18" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_USTreasuryAndGovernmentMember_019c76d5-3cfa-73cd-8ca7-b7811cbca9a1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_USTreasuryAndGovernmentMember"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_USStatesAndPoliticalSubdivisionsMember_019c76d5-3cfa-7ef7-b2d8-a2bdef4f34a0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_USStatesAndPoliticalSubdivisionsMember"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommercialMortgageBackedSecuritiesMember_019c76d5-3cfa-779f-9535-e2f42980123b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommercialMortgageBackedSecuritiesMember"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ResidentialMortgageBackedSecuritiesMember_019c76d5-3cfa-7eb0-bff1-b11bd6847943" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ResidentialMortgageBackedSecuritiesMember"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MortgageBackedSecuritiesIssuedByPrivateEnterprisesMember_019c76d5-3cfa-7670-9cd3-129d2ce41a35" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_MortgageBackedSecuritiesIssuedByPrivateEnterprisesMember"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherDebtSecuritiesMember_019de4c8-e5d2-707c-843d-b70192511f7b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherDebtSecuritiesMember"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue_019c76d5-3cfa-7d5c-aa8a-3592f4e485cb" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfHeldToMaturitySecuritiesLineItems_019c76d5-3cfa-7711-b300-92614709fa6e" xlink:to="loc_us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue_019c76d5-3cfa-7d5c-aa8a-3592f4e485cb" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss_019c76d5-3cfa-7699-9de5-c7a465878a96" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfHeldToMaturitySecuritiesLineItems_019c76d5-3cfa-7711-b300-92614709fa6e" xlink:to="loc_us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss_019c76d5-3cfa-7699-9de5-c7a465878a96" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue_019c76d5-3cfa-71e7-8428-178cea29981d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfHeldToMaturitySecuritiesLineItems_019c76d5-3cfa-7711-b300-92614709fa6e" xlink:to="loc_us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue_019c76d5-3cfa-71e7-8428-178cea29981d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss_019c76d5-3cfa-7511-81d2-f8c1c7ce8a4d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfHeldToMaturitySecuritiesLineItems_019c76d5-3cfa-7711-b300-92614709fa6e" xlink:to="loc_us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss_019c76d5-3cfa-7511-81d2-f8c1c7ce8a4d" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionFairValue_019de4da-9e54-794d-9452-a9b6349ed7dd" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfHeldToMaturitySecuritiesLineItems_019c76d5-3cfa-7711-b300-92614709fa6e" xlink:to="loc_us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionFairValue_019de4da-9e54-794d-9452-a9b6349ed7dd" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionAccumulatedLoss_019de4db-14c8-7a9c-b973-6634f4f54d0e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionAccumulatedLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfHeldToMaturitySecuritiesLineItems_019c76d5-3cfa-7711-b300-92614709fa6e" xlink:to="loc_us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionAccumulatedLoss_019de4db-14c8-7a9c-b973-6634f4f54d0e" xlink:type="arc" order="5"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.mtb.com/role/LoansandallowanceforloanlossesSummaryofCurrentPastDueandNonaccrualLoansDetail" xlink:type="simple" xlink:href="mtb-20260331.xsd#LoansandallowanceforloanlossesSummaryofCurrentPastDueandNonaccrualLoansDetail"/>
  <link:definitionLink xlink:role="http://www.mtb.com/role/LoansandallowanceforloanlossesSummaryofCurrentPastDueandNonaccrualLoansDetail" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentPastDueLineItems_019c76d5-3cfa-7627-a7fc-0d7da09dcd0a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableRecordedInvestmentPastDueLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfFinancingReceivablesPastDueTable_019c76d5-3cfa-7b62-8463-27e2f2a26a32" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfFinancingReceivablesPastDueTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentPastDueLineItems_019c76d5-3cfa-7627-a7fc-0d7da09dcd0a" xlink:to="loc_us-gaap_ScheduleOfFinancingReceivablesPastDueTable_019c76d5-3cfa-7b62-8463-27e2f2a26a32" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_019c76d5-3cfa-7001-bf8c-c2756df9d8e4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivablePortfolioSegmentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFinancingReceivablesPastDueTable_019c76d5-3cfa-7b62-8463-27e2f2a26a32" xlink:to="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_019c76d5-3cfa-7001-bf8c-c2756df9d8e4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019c76d5-3cfa-7001-bf8c-c2756df9d8e4_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivablePortfolioSegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_019c76d5-3cfa-7001-bf8c-c2756df9d8e4" xlink:to="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019c76d5-3cfa-7001-bf8c-c2756df9d8e4_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019c76d5-3cfa-7a05-9371-535fee3d53a0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivablePortfolioSegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_019c76d5-3cfa-7001-bf8c-c2756df9d8e4" xlink:to="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019c76d5-3cfa-7a05-9371-535fee3d53a0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommercialPortfolioSegmentMember_019c76d5-3cfa-75c5-a61b-a3ded93c8176" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommercialPortfolioSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019c76d5-3cfa-7a05-9371-535fee3d53a0" xlink:to="loc_us-gaap_CommercialPortfolioSegmentMember_019c76d5-3cfa-75c5-a61b-a3ded93c8176" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommercialRealEstatePortfolioSegmentMember_019c76d5-3cfa-7edf-87f2-27da52a1adcb" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommercialRealEstatePortfolioSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019c76d5-3cfa-7a05-9371-535fee3d53a0" xlink:to="loc_us-gaap_CommercialRealEstatePortfolioSegmentMember_019c76d5-3cfa-7edf-87f2-27da52a1adcb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ResidentialPortfolioSegmentMember_019c76d5-3cfa-7597-9be9-84c7270d4421" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ResidentialPortfolioSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019c76d5-3cfa-7a05-9371-535fee3d53a0" xlink:to="loc_us-gaap_ResidentialPortfolioSegmentMember_019c76d5-3cfa-7597-9be9-84c7270d4421" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConsumerPortfolioSegmentMember_019c76d5-3cfa-7eb1-bfd0-3028293dfec3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ConsumerPortfolioSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019c76d5-3cfa-7a05-9371-535fee3d53a0" xlink:to="loc_us-gaap_ConsumerPortfolioSegmentMember_019c76d5-3cfa-7eb1-bfd0-3028293dfec3" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_019c76d5-3cfa-7b17-a01d-660665c04090" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFinancingReceivablesPastDueTable_019c76d5-3cfa-7b62-8463-27e2f2a26a32" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_019c76d5-3cfa-7b17-a01d-660665c04090" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019c76d5-3cfa-7b17-a01d-660665c04090_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_019c76d5-3cfa-7b17-a01d-660665c04090" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019c76d5-3cfa-7b17-a01d-660665c04090_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019c76d5-3cfa-7a0e-8c42-c3dbee803502" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_019c76d5-3cfa-7b17-a01d-660665c04090" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019c76d5-3cfa-7a0e-8c42-c3dbee803502" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_CommercialRealEstateExcludingResidentialBuilderAndDeveloperAndOtherConstructionMember_019c76d5-3cfa-71bc-af6b-1048e0e35a69" xlink:href="mtb-20260331.xsd#mtb_CommercialRealEstateExcludingResidentialBuilderAndDeveloperAndOtherConstructionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019c76d5-3cfa-7a0e-8c42-c3dbee803502" xlink:to="loc_mtb_CommercialRealEstateExcludingResidentialBuilderAndDeveloperAndOtherConstructionMember_019c76d5-3cfa-71bc-af6b-1048e0e35a69" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_ResidentialBuilderAndDeveloperMember_019c76d5-3cfa-7bd9-b6f2-4a2f54196304" xlink:href="mtb-20260331.xsd#mtb_ResidentialBuilderAndDeveloperMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019c76d5-3cfa-7a0e-8c42-c3dbee803502" xlink:to="loc_mtb_ResidentialBuilderAndDeveloperMember_019c76d5-3cfa-7bd9-b6f2-4a2f54196304" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_OtherCommercialConstructionMember_019c76d5-3cfa-7bf7-8c71-d57c96c4b8d0" xlink:href="mtb-20260331.xsd#mtb_OtherCommercialConstructionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019c76d5-3cfa-7a0e-8c42-c3dbee803502" xlink:to="loc_mtb_OtherCommercialConstructionMember_019c76d5-3cfa-7bf7-8c71-d57c96c4b8d0" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_ResidentialRealEstateExcludingAltAMember_019c76d5-3cfa-7d96-baa8-5d13551715f0" xlink:href="mtb-20260331.xsd#mtb_ResidentialRealEstateExcludingAltAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019c76d5-3cfa-7a0e-8c42-c3dbee803502" xlink:to="loc_mtb_ResidentialRealEstateExcludingAltAMember_019c76d5-3cfa-7d96-baa8-5d13551715f0" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_HomeEquityLinesAndLoansMember_019c76d5-3cfa-78d6-936f-28742d609762" xlink:href="mtb-20260331.xsd#mtb_HomeEquityLinesAndLoansMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019c76d5-3cfa-7a0e-8c42-c3dbee803502" xlink:to="loc_mtb_HomeEquityLinesAndLoansMember_019c76d5-3cfa-78d6-936f-28742d609762" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_RecreationalFinanceMember_019c76d5-3cfa-799e-a93f-e8d188d6991e" xlink:href="mtb-20260331.xsd#mtb_RecreationalFinanceMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019c76d5-3cfa-7a0e-8c42-c3dbee803502" xlink:to="loc_mtb_RecreationalFinanceMember_019c76d5-3cfa-799e-a93f-e8d188d6991e" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AutomobileLoanMember_019c76d5-3cfa-7c36-920e-cbde276bf9ad" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AutomobileLoanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019c76d5-3cfa-7a0e-8c42-c3dbee803502" xlink:to="loc_us-gaap_AutomobileLoanMember_019c76d5-3cfa-7c36-920e-cbde276bf9ad" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConsumerOtherMember_019c76d5-3cfa-7c1a-8199-b70bb35e82b5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ConsumerOtherMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019c76d5-3cfa-7a0e-8c42-c3dbee803502" xlink:to="loc_us-gaap_ConsumerOtherMember_019c76d5-3cfa-7c1a-8199-b70bb35e82b5" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivablesPeriodPastDueAxis_019c76d5-3cfa-70a5-8fbc-e81d642330f2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivablesPeriodPastDueAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFinancingReceivablesPastDueTable_019c76d5-3cfa-7b62-8463-27e2f2a26a32" xlink:to="loc_us-gaap_FinancingReceivablesPeriodPastDueAxis_019c76d5-3cfa-70a5-8fbc-e81d642330f2" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivablesPeriodPastDueDomain_019c76d5-3cfa-70a5-8fbc-e81d642330f2_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivablesPeriodPastDueDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancingReceivablesPeriodPastDueAxis_019c76d5-3cfa-70a5-8fbc-e81d642330f2" xlink:to="loc_us-gaap_FinancingReceivablesPeriodPastDueDomain_019c76d5-3cfa-70a5-8fbc-e81d642330f2_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivablesPeriodPastDueDomain_019c76d5-3cfa-72b3-be61-d97359ddba77" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivablesPeriodPastDueDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancingReceivablesPeriodPastDueAxis_019c76d5-3cfa-70a5-8fbc-e81d642330f2" xlink:to="loc_us-gaap_FinancingReceivablesPeriodPastDueDomain_019c76d5-3cfa-72b3-be61-d97359ddba77" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialAssetNotPastDueMember_019c76d5-3cfa-78cd-886a-a986c27e3cb8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancialAssetNotPastDueMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivablesPeriodPastDueDomain_019c76d5-3cfa-72b3-be61-d97359ddba77" xlink:to="loc_us-gaap_FinancialAssetNotPastDueMember_019c76d5-3cfa-78cd-886a-a986c27e3cb8" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivables30To59DaysPastDueMember_019c76d5-3cfa-7928-84ed-d4d77a680d63" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivables30To59DaysPastDueMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivablesPeriodPastDueDomain_019c76d5-3cfa-72b3-be61-d97359ddba77" xlink:to="loc_us-gaap_FinancingReceivables30To59DaysPastDueMember_019c76d5-3cfa-7928-84ed-d4d77a680d63" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivablesEqualToGreaterThan90DaysPastDueMember_019c76d5-3cfa-77b7-b30d-8613c3cabfd2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivablesEqualToGreaterThan90DaysPastDueMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivablesPeriodPastDueDomain_019c76d5-3cfa-72b3-be61-d97359ddba77" xlink:to="loc_us-gaap_FinancingReceivablesEqualToGreaterThan90DaysPastDueMember_019c76d5-3cfa-77b7-b30d-8613c3cabfd2" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestBeforeAllowanceForCreditLoss_019c76d5-3cfa-7982-9eac-8a9cd854c8d3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestBeforeAllowanceForCreditLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentPastDueLineItems_019c76d5-3cfa-7627-a7fc-0d7da09dcd0a" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterestBeforeAllowanceForCreditLoss_019c76d5-3cfa-7982-9eac-8a9cd854c8d3" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestNonaccrual_019c76d5-3cfa-7099-befb-1bc27811cd97" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestNonaccrual"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentPastDueLineItems_019c76d5-3cfa-7627-a7fc-0d7da09dcd0a" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterestNonaccrual_019c76d5-3cfa-7099-befb-1bc27811cd97" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestBeforeAllowanceForCreditLossFeeAndLoanInProcess_019c76d5-3cfa-70c1-9a37-12677f95e31f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestBeforeAllowanceForCreditLossFeeAndLoanInProcess"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentPastDueLineItems_019c76d5-3cfa-7627-a7fc-0d7da09dcd0a" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterestBeforeAllowanceForCreditLossFeeAndLoanInProcess_019c76d5-3cfa-70c1-9a37-12677f95e31f" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableUnamortizedLoanCommitmentOriginationFeeAndPremiumDiscount_019c76d5-3cfa-784c-8e33-b233d097369f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableUnamortizedLoanCommitmentOriginationFeeAndPremiumDiscount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentPastDueLineItems_019c76d5-3cfa-7627-a7fc-0d7da09dcd0a" xlink:to="loc_us-gaap_FinancingReceivableUnamortizedLoanCommitmentOriginationFeeAndPremiumDiscount_019c76d5-3cfa-784c-8e33-b233d097369f" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableAccruedInterestBeforeAllowanceForCreditLoss_019c76d5-3cfa-7b26-9674-9c01a4be3b1a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableAccruedInterestBeforeAllowanceForCreditLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentPastDueLineItems_019c76d5-3cfa-7627-a7fc-0d7da09dcd0a" xlink:to="loc_us-gaap_FinancingReceivableAccruedInterestBeforeAllowanceForCreditLoss_019c76d5-3cfa-7b26-9674-9c01a4be3b1a" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LoansReceivableHeldForSaleNetNotPartOfDisposalGroup_019c76d5-3cfa-7864-829e-6aab4b21eb2f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LoansReceivableHeldForSaleNetNotPartOfDisposalGroup"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentPastDueLineItems_019c76d5-3cfa-7627-a7fc-0d7da09dcd0a" xlink:to="loc_us-gaap_LoansReceivableHeldForSaleNetNotPartOfDisposalGroup_019c76d5-3cfa-7864-829e-6aab4b21eb2f" xlink:type="arc" order="5"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.mtb.com/role/LoansandallowanceforloanlossesAdditionalInformationDetail" xlink:type="simple" xlink:href="mtb-20260331.xsd#LoansandallowanceforloanlossesAdditionalInformationDetail"/>
  <link:definitionLink xlink:role="http://www.mtb.com/role/LoansandallowanceforloanlossesAdditionalInformationDetail" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_mtb_LoansAndLeasesReceivableLineItems_019c76d5-3cfa-7f6d-ae2d-0b1e00963418" xlink:href="mtb-20260331.xsd#mtb_LoansAndLeasesReceivableLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_LoansAndLeasesReceivableTable_019c76d5-3cfa-7edf-9324-e9c8590ac34e" xlink:href="mtb-20260331.xsd#mtb_LoansAndLeasesReceivableTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_mtb_LoansAndLeasesReceivableLineItems_019c76d5-3cfa-7f6d-ae2d-0b1e00963418" xlink:to="loc_mtb_LoansAndLeasesReceivableTable_019c76d5-3cfa-7edf-9324-e9c8590ac34e" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_019c76d5-3cfa-7273-8c9f-1375d17f0d4b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_mtb_LoansAndLeasesReceivableTable_019c76d5-3cfa-7edf-9324-e9c8590ac34e" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_019c76d5-3cfa-7273-8c9f-1375d17f0d4b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019c76d5-3cfa-7273-8c9f-1375d17f0d4b_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_019c76d5-3cfa-7273-8c9f-1375d17f0d4b" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019c76d5-3cfa-7273-8c9f-1375d17f0d4b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019c76d5-3cfa-7da7-9ad8-de4dde4be2e0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_019c76d5-3cfa-7273-8c9f-1375d17f0d4b" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019c76d5-3cfa-7da7-9ad8-de4dde4be2e0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_HomeEquityLinesAndLoansMember_019c76d5-3cfa-7101-a7a4-59679b867fcd" xlink:href="mtb-20260331.xsd#mtb_HomeEquityLinesAndLoansMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019c76d5-3cfa-7da7-9ad8-de4dde4be2e0" xlink:to="loc_mtb_HomeEquityLinesAndLoansMember_019c76d5-3cfa-7101-a7a4-59679b867fcd" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConsumerOtherMember_019c76d5-3cfa-7e19-925d-60d9b09e1883" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ConsumerOtherMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019c76d5-3cfa-7da7-9ad8-de4dde4be2e0" xlink:to="loc_us-gaap_ConsumerOtherMember_019c76d5-3cfa-7e19-925d-60d9b09e1883" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_019c76d5-3cfa-7db8-a8b9-3bb9d244ac64" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivablePortfolioSegmentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_mtb_LoansAndLeasesReceivableTable_019c76d5-3cfa-7edf-9324-e9c8590ac34e" xlink:to="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_019c76d5-3cfa-7db8-a8b9-3bb9d244ac64" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019c76d5-3cfa-7db8-a8b9-3bb9d244ac64_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivablePortfolioSegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_019c76d5-3cfa-7db8-a8b9-3bb9d244ac64" xlink:to="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019c76d5-3cfa-7db8-a8b9-3bb9d244ac64_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019c76d5-3cfa-7226-861e-db318c30dd84" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivablePortfolioSegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_019c76d5-3cfa-7db8-a8b9-3bb9d244ac64" xlink:to="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019c76d5-3cfa-7226-861e-db318c30dd84" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommercialPortfolioSegmentMember_019c76d5-3cfa-7325-bdf8-05d0c0372d6c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommercialPortfolioSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019c76d5-3cfa-7226-861e-db318c30dd84" xlink:to="loc_us-gaap_CommercialPortfolioSegmentMember_019c76d5-3cfa-7325-bdf8-05d0c0372d6c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommercialRealEstatePortfolioSegmentMember_019c76d5-3cfa-7a83-a190-0c550ecfa0c9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommercialRealEstatePortfolioSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019c76d5-3cfa-7226-861e-db318c30dd84" xlink:to="loc_us-gaap_CommercialRealEstatePortfolioSegmentMember_019c76d5-3cfa-7a83-a190-0c550ecfa0c9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ResidentialPortfolioSegmentMember_019c76d5-3cfa-7192-8b72-545098f8ad16" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ResidentialPortfolioSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019c76d5-3cfa-7226-861e-db318c30dd84" xlink:to="loc_us-gaap_ResidentialPortfolioSegmentMember_019c76d5-3cfa-7192-8b72-545098f8ad16" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConsumerPortfolioSegmentMember_019c76d5-3cfa-701c-a287-60c4cbf6b5f7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ConsumerPortfolioSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019c76d5-3cfa-7226-861e-db318c30dd84" xlink:to="loc_us-gaap_ConsumerPortfolioSegmentMember_019c76d5-3cfa-701c-a287-60c4cbf6b5f7" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_ResidentialBuilderAndDeveloperMember_019c76d5-3cfa-7293-a698-6bcffeff4cde" xlink:href="mtb-20260331.xsd#mtb_ResidentialBuilderAndDeveloperMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019c76d5-3cfa-7226-861e-db318c30dd84" xlink:to="loc_mtb_ResidentialBuilderAndDeveloperMember_019c76d5-3cfa-7293-a698-6bcffeff4cde" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PledgedStatusAxis_019c76d5-3cfa-73f2-a9b0-d887ac32984f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PledgedStatusAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_mtb_LoansAndLeasesReceivableTable_019c76d5-3cfa-7edf-9324-e9c8590ac34e" xlink:to="loc_us-gaap_PledgedStatusAxis_019c76d5-3cfa-73f2-a9b0-d887ac32984f" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PledgedStatusDomain_019c76d5-3cfa-73f2-a9b0-d887ac32984f_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PledgedStatusDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PledgedStatusAxis_019c76d5-3cfa-73f2-a9b0-d887ac32984f" xlink:to="loc_us-gaap_PledgedStatusDomain_019c76d5-3cfa-73f2-a9b0-d887ac32984f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PledgedStatusDomain_019c76d5-3cfa-76e0-b66f-161723726e23" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PledgedStatusDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PledgedStatusAxis_019c76d5-3cfa-73f2-a9b0-d887ac32984f" xlink:to="loc_us-gaap_PledgedStatusDomain_019c76d5-3cfa-76e0-b66f-161723726e23" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetPledgedAsCollateralWithoutRightMember_019c76d5-3cfa-72c3-9628-5ef20e5a41af" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AssetPledgedAsCollateralWithoutRightMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PledgedStatusDomain_019c76d5-3cfa-76e0-b66f-161723726e23" xlink:to="loc_us-gaap_AssetPledgedAsCollateralWithoutRightMember_019c76d5-3cfa-72c3-9628-5ef20e5a41af" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PledgingPurposeAxis_019c76d5-3cfa-7a99-8092-b2ea4eb37d6d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PledgingPurposeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_mtb_LoansAndLeasesReceivableTable_019c76d5-3cfa-7edf-9324-e9c8590ac34e" xlink:to="loc_us-gaap_PledgingPurposeAxis_019c76d5-3cfa-7a99-8092-b2ea4eb37d6d" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PledgingPurposeDomain_019c76d5-3cfa-7a99-8092-b2ea4eb37d6d_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PledgingPurposeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PledgingPurposeAxis_019c76d5-3cfa-7a99-8092-b2ea4eb37d6d" xlink:to="loc_us-gaap_PledgingPurposeDomain_019c76d5-3cfa-7a99-8092-b2ea4eb37d6d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PledgingPurposeDomain_019c76d5-3cfa-7190-9135-63194f94e3c2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PledgingPurposeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PledgingPurposeAxis_019c76d5-3cfa-7a99-8092-b2ea4eb37d6d" xlink:to="loc_us-gaap_PledgingPurposeDomain_019c76d5-3cfa-7190-9135-63194f94e3c2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FederalHomeLoanBankAdvancesMember_019c76d5-3cfa-7797-aaa5-48e658ca3f82" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FederalHomeLoanBankAdvancesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PledgingPurposeDomain_019c76d5-3cfa-7190-9135-63194f94e3c2" xlink:to="loc_us-gaap_FederalHomeLoanBankAdvancesMember_019c76d5-3cfa-7797-aaa5-48e658ca3f82" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_ResidentialMortgageLoansSecuredByResidentialRealEstateInProcessOfForeclosure_019c76d5-3cfa-7d8b-a03a-f54f8ffa6f53" xlink:href="mtb-20260331.xsd#mtb_ResidentialMortgageLoansSecuredByResidentialRealEstateInProcessOfForeclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_mtb_LoansAndLeasesReceivableLineItems_019c76d5-3cfa-7f6d-ae2d-0b1e00963418" xlink:to="loc_mtb_ResidentialMortgageLoansSecuredByResidentialRealEstateInProcessOfForeclosure_019c76d5-3cfa-7d8b-a03a-f54f8ffa6f53" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_PercentageOfLoansInTheProcessOfForeclosureServicedByOtherEntitiesClassifiedAsGovernmentGuaranteed_019c76d5-3cfa-75fb-b7fb-3b244a743a77" xlink:href="mtb-20260331.xsd#mtb_PercentageOfLoansInTheProcessOfForeclosureServicedByOtherEntitiesClassifiedAsGovernmentGuaranteed"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_mtb_LoansAndLeasesReceivableLineItems_019c76d5-3cfa-7f6d-ae2d-0b1e00963418" xlink:to="loc_mtb_PercentageOfLoansInTheProcessOfForeclosureServicedByOtherEntitiesClassifiedAsGovernmentGuaranteed_019c76d5-3cfa-75fb-b7fb-3b244a743a77" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NotesReceivableGross_019c76d5-3cfa-75f6-b2e5-af4b932e1df4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NotesReceivableGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_mtb_LoansAndLeasesReceivableLineItems_019c76d5-3cfa-7f6d-ae2d-0b1e00963418" xlink:to="loc_us-gaap_NotesReceivableGross_019c76d5-3cfa-75f6-b2e5-af4b932e1df4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NotesReceivableNet_019c76d5-3cfa-792a-b692-5c86ad171803" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NotesReceivableNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_mtb_LoansAndLeasesReceivableLineItems_019c76d5-3cfa-7f6d-ae2d-0b1e00963418" xlink:to="loc_us-gaap_NotesReceivableNet_019c76d5-3cfa-792a-b692-5c86ad171803" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableAccruedInterestBeforeAllowanceForCreditLoss_019c76d5-3cfa-70bc-9434-d4ce3fa64a47" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableAccruedInterestBeforeAllowanceForCreditLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_mtb_LoansAndLeasesReceivableLineItems_019c76d5-3cfa-7f6d-ae2d-0b1e00963418" xlink:to="loc_us-gaap_FinancingReceivableAccruedInterestBeforeAllowanceForCreditLoss_019c76d5-3cfa-70bc-9434-d4ce3fa64a47" xlink:type="arc" order="4"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.mtb.com/role/LoansandallowanceforloanlossesSummaryofLoangradesappliedvariousclassesofCommercialandRealEstateLoansDetail" xlink:type="simple" xlink:href="mtb-20260331.xsd#LoansandallowanceforloanlossesSummaryofLoangradesappliedvariousclassesofCommercialandRealEstateLoansDetail"/>
  <link:definitionLink xlink:role="http://www.mtb.com/role/LoansandallowanceforloanlossesSummaryofLoangradesappliedvariousclassesofCommercialandRealEstateLoansDetail" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentLineItems_019c76d5-3cfa-7f06-872f-dc33cddfe94d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableRecordedInvestmentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfFinancingReceivableRecordedInvestmentCreditQualityIndicatorTable_019c76d5-3cfa-7d2e-acca-9fbb14c8410b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfFinancingReceivableRecordedInvestmentCreditQualityIndicatorTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentLineItems_019c76d5-3cfa-7f06-872f-dc33cddfe94d" xlink:to="loc_us-gaap_ScheduleOfFinancingReceivableRecordedInvestmentCreditQualityIndicatorTable_019c76d5-3cfa-7d2e-acca-9fbb14c8410b" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_019c76d5-3cfa-789c-9c6d-cb57a286d5c5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivablePortfolioSegmentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFinancingReceivableRecordedInvestmentCreditQualityIndicatorTable_019c76d5-3cfa-7d2e-acca-9fbb14c8410b" xlink:to="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_019c76d5-3cfa-789c-9c6d-cb57a286d5c5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019c76d5-3cfa-789c-9c6d-cb57a286d5c5_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivablePortfolioSegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_019c76d5-3cfa-789c-9c6d-cb57a286d5c5" xlink:to="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019c76d5-3cfa-789c-9c6d-cb57a286d5c5_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019c76d5-3cfa-7a56-a3f0-db1630b7a227" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivablePortfolioSegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_019c76d5-3cfa-789c-9c6d-cb57a286d5c5" xlink:to="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019c76d5-3cfa-7a56-a3f0-db1630b7a227" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommercialPortfolioSegmentMember_019c76d5-3cfa-74f6-8dbf-37b98d3715e7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommercialPortfolioSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019c76d5-3cfa-7a56-a3f0-db1630b7a227" xlink:to="loc_us-gaap_CommercialPortfolioSegmentMember_019c76d5-3cfa-74f6-8dbf-37b98d3715e7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommercialRealEstatePortfolioSegmentMember_019c76d5-3cfa-7cb1-bc1d-c85131eaab4f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommercialRealEstatePortfolioSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019c76d5-3cfa-7a56-a3f0-db1630b7a227" xlink:to="loc_us-gaap_CommercialRealEstatePortfolioSegmentMember_019c76d5-3cfa-7cb1-bc1d-c85131eaab4f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_019c76d5-3cfa-762c-a223-5bc930d1cc62" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFinancingReceivableRecordedInvestmentCreditQualityIndicatorTable_019c76d5-3cfa-7d2e-acca-9fbb14c8410b" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_019c76d5-3cfa-762c-a223-5bc930d1cc62" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019c76d5-3cfa-762c-a223-5bc930d1cc62_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_019c76d5-3cfa-762c-a223-5bc930d1cc62" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019c76d5-3cfa-762c-a223-5bc930d1cc62_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019c76d5-3cfa-77bc-989b-feedc844dc0e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_019c76d5-3cfa-762c-a223-5bc930d1cc62" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019c76d5-3cfa-77bc-989b-feedc844dc0e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_CommercialRealEstateExcludingResidentialBuilderAndDeveloperAndOtherConstructionMember_019c76d5-3cfa-71e0-93e1-a1ba70559e62" xlink:href="mtb-20260331.xsd#mtb_CommercialRealEstateExcludingResidentialBuilderAndDeveloperAndOtherConstructionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019c76d5-3cfa-77bc-989b-feedc844dc0e" xlink:to="loc_mtb_CommercialRealEstateExcludingResidentialBuilderAndDeveloperAndOtherConstructionMember_019c76d5-3cfa-71e0-93e1-a1ba70559e62" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_ResidentialBuilderAndDeveloperMember_019c76d5-3cfa-7988-ac63-e6921c217da6" xlink:href="mtb-20260331.xsd#mtb_ResidentialBuilderAndDeveloperMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019c76d5-3cfa-77bc-989b-feedc844dc0e" xlink:to="loc_mtb_ResidentialBuilderAndDeveloperMember_019c76d5-3cfa-7988-ac63-e6921c217da6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_OtherCommercialConstructionMember_019c76d5-3cfa-73b8-adf8-aed3bf281da3" xlink:href="mtb-20260331.xsd#mtb_OtherCommercialConstructionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019c76d5-3cfa-77bc-989b-feedc844dc0e" xlink:to="loc_mtb_OtherCommercialConstructionMember_019c76d5-3cfa-73b8-adf8-aed3bf281da3" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InternalCreditAssessmentAxis_019c76d5-3cfa-78b2-8e17-e9fb27101187" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InternalCreditAssessmentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFinancingReceivableRecordedInvestmentCreditQualityIndicatorTable_019c76d5-3cfa-7d2e-acca-9fbb14c8410b" xlink:to="loc_us-gaap_InternalCreditAssessmentAxis_019c76d5-3cfa-78b2-8e17-e9fb27101187" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InternalCreditAssessmentDomain_019c76d5-3cfa-78b2-8e17-e9fb27101187_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InternalCreditAssessmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_InternalCreditAssessmentAxis_019c76d5-3cfa-78b2-8e17-e9fb27101187" xlink:to="loc_us-gaap_InternalCreditAssessmentDomain_019c76d5-3cfa-78b2-8e17-e9fb27101187_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InternalCreditAssessmentDomain_019c76d5-3cfa-7279-81a6-064c923883ea" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InternalCreditAssessmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_InternalCreditAssessmentAxis_019c76d5-3cfa-78b2-8e17-e9fb27101187" xlink:to="loc_us-gaap_InternalCreditAssessmentDomain_019c76d5-3cfa-7279-81a6-064c923883ea" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PassMember_019c76d5-3cfa-7fa3-9cb4-b81c3ce3315b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PassMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InternalCreditAssessmentDomain_019c76d5-3cfa-7279-81a6-064c923883ea" xlink:to="loc_us-gaap_PassMember_019c76d5-3cfa-7fa3-9cb4-b81c3ce3315b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_CriticizedAccrualMember_019c76d5-3cfa-7c61-b412-9c5664eeba48" xlink:href="mtb-20260331.xsd#mtb_CriticizedAccrualMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InternalCreditAssessmentDomain_019c76d5-3cfa-7279-81a6-064c923883ea" xlink:to="loc_mtb_CriticizedAccrualMember_019c76d5-3cfa-7c61-b412-9c5664eeba48" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_CriticizedNonaccrualMember_019c76d5-3cfa-7735-9477-736ee10fd659" xlink:href="mtb-20260331.xsd#mtb_CriticizedNonaccrualMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InternalCreditAssessmentDomain_019c76d5-3cfa-7279-81a6-064c923883ea" xlink:to="loc_mtb_CriticizedNonaccrualMember_019c76d5-3cfa-7735-9477-736ee10fd659" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestYearOneOriginatedCurrentFiscalYear_019c76d5-3cfa-7f3e-b5a5-dcb88486e7e3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestYearOneOriginatedCurrentFiscalYear"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentLineItems_019c76d5-3cfa-7f06-872f-dc33cddfe94d" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterestYearOneOriginatedCurrentFiscalYear_019c76d5-3cfa-7f3e-b5a5-dcb88486e7e3" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestYearTwoOriginatedFiscalYearBeforeCurrentFiscalYear_019c76d5-3cfa-7040-a36f-29e0ddc6d0da" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestYearTwoOriginatedFiscalYearBeforeCurrentFiscalYear"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentLineItems_019c76d5-3cfa-7f06-872f-dc33cddfe94d" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterestYearTwoOriginatedFiscalYearBeforeCurrentFiscalYear_019c76d5-3cfa-7040-a36f-29e0ddc6d0da" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestYearThreeOriginatedTwoYearsBeforeCurrentFiscalYear_019c76d5-3cfa-7abd-b151-df2c8bd20131" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestYearThreeOriginatedTwoYearsBeforeCurrentFiscalYear"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentLineItems_019c76d5-3cfa-7f06-872f-dc33cddfe94d" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterestYearThreeOriginatedTwoYearsBeforeCurrentFiscalYear_019c76d5-3cfa-7abd-b151-df2c8bd20131" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestYearFourOriginatedThreeYearsBeforeCurrentFiscalYear_019c76d5-3cfa-7997-a3f6-4b2ce26b31b7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestYearFourOriginatedThreeYearsBeforeCurrentFiscalYear"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentLineItems_019c76d5-3cfa-7f06-872f-dc33cddfe94d" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterestYearFourOriginatedThreeYearsBeforeCurrentFiscalYear_019c76d5-3cfa-7997-a3f6-4b2ce26b31b7" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestYearFiveOriginatedFourYearsBeforeCurrentFiscalYear_019c76d5-3cfa-734b-9f16-6e0fa58dcea9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestYearFiveOriginatedFourYearsBeforeCurrentFiscalYear"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentLineItems_019c76d5-3cfa-7f06-872f-dc33cddfe94d" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterestYearFiveOriginatedFourYearsBeforeCurrentFiscalYear_019c76d5-3cfa-734b-9f16-6e0fa58dcea9" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestOriginatedMoreThanFiveYearsBeforeCurrentFiscalYear_019c76d5-3cfa-79af-95fb-a6e9b8cf6b39" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestOriginatedMoreThanFiveYearsBeforeCurrentFiscalYear"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentLineItems_019c76d5-3cfa-7f06-872f-dc33cddfe94d" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterestOriginatedMoreThanFiveYearsBeforeCurrentFiscalYear_019c76d5-3cfa-79af-95fb-a6e9b8cf6b39" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestRevolving_019c76d5-3cfa-7606-9500-5142eda84398" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestRevolving"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentLineItems_019c76d5-3cfa-7f06-872f-dc33cddfe94d" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterestRevolving_019c76d5-3cfa-7606-9500-5142eda84398" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestRevolvingConvertedToTermLoan_019c76d5-3cfa-7c8a-a7b3-2b2821e741d1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestRevolvingConvertedToTermLoan"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentLineItems_019c76d5-3cfa-7f06-872f-dc33cddfe94d" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterestRevolvingConvertedToTermLoan_019c76d5-3cfa-7c8a-a7b3-2b2821e741d1" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestBeforeAllowanceForCreditLossFeeAndLoanInProcess_019c76d5-3cfa-7274-91bb-e9adac2e2328" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestBeforeAllowanceForCreditLossFeeAndLoanInProcess"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentLineItems_019c76d5-3cfa-7f06-872f-dc33cddfe94d" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterestBeforeAllowanceForCreditLossFeeAndLoanInProcess_019c76d5-3cfa-7274-91bb-e9adac2e2328" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestAllowanceForCreditLossWriteoffByOriginationYearAbstract_019c76d5-3cfa-7d97-95ef-a6788f1cbded" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestAllowanceForCreditLossWriteoffByOriginationYearAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentLineItems_019c76d5-3cfa-7f06-872f-dc33cddfe94d" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterestAllowanceForCreditLossWriteoffByOriginationYearAbstract_019c76d5-3cfa-7d97-95ef-a6788f1cbded" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestYearOneOriginatedCurrentFiscalYearWriteoff_019c76d5-3cfa-7252-be8d-2bfc9f13dfc2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestYearOneOriginatedCurrentFiscalYearWriteoff"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableExcludingAccruedInterestAllowanceForCreditLossWriteoffByOriginationYearAbstract_019c76d5-3cfa-7d97-95ef-a6788f1cbded" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterestYearOneOriginatedCurrentFiscalYearWriteoff_019c76d5-3cfa-7252-be8d-2bfc9f13dfc2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestYearTwoOriginatedFiscalYearBeforeCurrentFiscalYearWriteoff_019c76d5-3cfa-7a85-88e7-e8c07762c268" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestYearTwoOriginatedFiscalYearBeforeCurrentFiscalYearWriteoff"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableExcludingAccruedInterestAllowanceForCreditLossWriteoffByOriginationYearAbstract_019c76d5-3cfa-7d97-95ef-a6788f1cbded" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterestYearTwoOriginatedFiscalYearBeforeCurrentFiscalYearWriteoff_019c76d5-3cfa-7a85-88e7-e8c07762c268" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestYearThreeOriginatedTwoYearsBeforeCurrentFiscalYearWriteoff_019c76d5-3cfa-7d13-8062-9b069a01c9a0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestYearThreeOriginatedTwoYearsBeforeCurrentFiscalYearWriteoff"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableExcludingAccruedInterestAllowanceForCreditLossWriteoffByOriginationYearAbstract_019c76d5-3cfa-7d97-95ef-a6788f1cbded" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterestYearThreeOriginatedTwoYearsBeforeCurrentFiscalYearWriteoff_019c76d5-3cfa-7d13-8062-9b069a01c9a0" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestYearFourOriginatedThreeYearsBeforeCurrentFiscalYearWriteoff_019c76d5-3cfa-7659-963f-6254faaff06d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestYearFourOriginatedThreeYearsBeforeCurrentFiscalYearWriteoff"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableExcludingAccruedInterestAllowanceForCreditLossWriteoffByOriginationYearAbstract_019c76d5-3cfa-7d97-95ef-a6788f1cbded" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterestYearFourOriginatedThreeYearsBeforeCurrentFiscalYearWriteoff_019c76d5-3cfa-7659-963f-6254faaff06d" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestYearFiveOriginatedFourYearsBeforeCurrentFiscalYearWriteoff_019c76d5-3cfa-7fba-af06-945dfbcbfbaf" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestYearFiveOriginatedFourYearsBeforeCurrentFiscalYearWriteoff"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableExcludingAccruedInterestAllowanceForCreditLossWriteoffByOriginationYearAbstract_019c76d5-3cfa-7d97-95ef-a6788f1cbded" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterestYearFiveOriginatedFourYearsBeforeCurrentFiscalYearWriteoff_019c76d5-3cfa-7fba-af06-945dfbcbfbaf" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestOriginatedMoreThanFiveYearsBeforeCurrentFiscalYearWriteoff_019c76d5-3cfa-7bca-9233-fd0198a7a491" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestOriginatedMoreThanFiveYearsBeforeCurrentFiscalYearWriteoff"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableExcludingAccruedInterestAllowanceForCreditLossWriteoffByOriginationYearAbstract_019c76d5-3cfa-7d97-95ef-a6788f1cbded" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterestOriginatedMoreThanFiveYearsBeforeCurrentFiscalYearWriteoff_019c76d5-3cfa-7bca-9233-fd0198a7a491" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestRevolvingWriteoff_019c76d5-3cfa-73d1-aeb5-121e77c04e83" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestRevolvingWriteoff"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableExcludingAccruedInterestAllowanceForCreditLossWriteoffByOriginationYearAbstract_019c76d5-3cfa-7d97-95ef-a6788f1cbded" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterestRevolvingWriteoff_019c76d5-3cfa-73d1-aeb5-121e77c04e83" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestRevolvingConvertedToTermLoanWriteoff_019c76d5-3cfa-7ebf-8f61-322ae002bca2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestRevolvingConvertedToTermLoanWriteoff"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableExcludingAccruedInterestAllowanceForCreditLossWriteoffByOriginationYearAbstract_019c76d5-3cfa-7d97-95ef-a6788f1cbded" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterestRevolvingConvertedToTermLoanWriteoff_019c76d5-3cfa-7ebf-8f61-322ae002bca2" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestAllowanceForCreditLossWriteoff_019c76d5-3cfa-71db-b0df-7b206bdfc967" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestAllowanceForCreditLossWriteoff"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableExcludingAccruedInterestAllowanceForCreditLossWriteoffByOriginationYearAbstract_019c76d5-3cfa-7d97-95ef-a6788f1cbded" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterestAllowanceForCreditLossWriteoff_019c76d5-3cfa-71db-b0df-7b206bdfc967" xlink:type="arc" order="9"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.mtb.com/role/LoansandallowanceforloanlossesSummaryofloansinAccrualandNonaccrualStatusDetail" xlink:type="simple" xlink:href="mtb-20260331.xsd#LoansandallowanceforloanlossesSummaryofloansinAccrualandNonaccrualStatusDetail"/>
  <link:definitionLink xlink:role="http://www.mtb.com/role/LoansandallowanceforloanlossesSummaryofloansinAccrualandNonaccrualStatusDetail" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentLineItems_019c76d5-3cfa-7d28-9fe8-8b741d5f3924" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableRecordedInvestmentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfFinancingReceivableRecordedInvestmentCreditQualityIndicatorTable_019c76d5-3cfa-71fc-a963-f0dda61bb3d6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfFinancingReceivableRecordedInvestmentCreditQualityIndicatorTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentLineItems_019c76d5-3cfa-7d28-9fe8-8b741d5f3924" xlink:to="loc_us-gaap_ScheduleOfFinancingReceivableRecordedInvestmentCreditQualityIndicatorTable_019c76d5-3cfa-71fc-a963-f0dda61bb3d6" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivablesPeriodPastDueAxis_019c76d5-3cfa-702c-8a36-cae82e0e1cc7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivablesPeriodPastDueAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFinancingReceivableRecordedInvestmentCreditQualityIndicatorTable_019c76d5-3cfa-71fc-a963-f0dda61bb3d6" xlink:to="loc_us-gaap_FinancingReceivablesPeriodPastDueAxis_019c76d5-3cfa-702c-8a36-cae82e0e1cc7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivablesPeriodPastDueDomain_019c76d5-3cfa-702c-8a36-cae82e0e1cc7_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivablesPeriodPastDueDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancingReceivablesPeriodPastDueAxis_019c76d5-3cfa-702c-8a36-cae82e0e1cc7" xlink:to="loc_us-gaap_FinancingReceivablesPeriodPastDueDomain_019c76d5-3cfa-702c-8a36-cae82e0e1cc7_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivablesPeriodPastDueDomain_019c76d5-3cfa-7de0-9103-696cc247bf65" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivablesPeriodPastDueDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancingReceivablesPeriodPastDueAxis_019c76d5-3cfa-702c-8a36-cae82e0e1cc7" xlink:to="loc_us-gaap_FinancingReceivablesPeriodPastDueDomain_019c76d5-3cfa-7de0-9103-696cc247bf65" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialAssetNotPastDueMember_019c76d5-3cfa-77a5-ab37-473e0bf38bae" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancialAssetNotPastDueMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivablesPeriodPastDueDomain_019c76d5-3cfa-7de0-9103-696cc247bf65" xlink:to="loc_us-gaap_FinancialAssetNotPastDueMember_019c76d5-3cfa-77a5-ab37-473e0bf38bae" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_FinancialAsset30To89DaysPastDueMember_019c76d5-3cfa-77b8-acd1-6a0f4e235c4f" xlink:href="mtb-20260331.xsd#mtb_FinancialAsset30To89DaysPastDueMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivablesPeriodPastDueDomain_019c76d5-3cfa-7de0-9103-696cc247bf65" xlink:to="loc_mtb_FinancialAsset30To89DaysPastDueMember_019c76d5-3cfa-77b8-acd1-6a0f4e235c4f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivablesEqualToGreaterThan90DaysPastDueMember_019c76d5-3cfa-739f-a1fb-386ebe149d23" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivablesEqualToGreaterThan90DaysPastDueMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivablesPeriodPastDueDomain_019c76d5-3cfa-7de0-9103-696cc247bf65" xlink:to="loc_us-gaap_FinancingReceivablesEqualToGreaterThan90DaysPastDueMember_019c76d5-3cfa-739f-a1fb-386ebe149d23" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_NonaccrualMember_019c76d5-3cfa-73c4-b914-91e0f7d59bbe" xlink:href="mtb-20260331.xsd#mtb_NonaccrualMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivablesPeriodPastDueDomain_019c76d5-3cfa-7de0-9103-696cc247bf65" xlink:to="loc_mtb_NonaccrualMember_019c76d5-3cfa-73c4-b914-91e0f7d59bbe" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_019c76d5-3cfa-75f7-af34-19f6171ae968" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFinancingReceivableRecordedInvestmentCreditQualityIndicatorTable_019c76d5-3cfa-71fc-a963-f0dda61bb3d6" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_019c76d5-3cfa-75f7-af34-19f6171ae968" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019c76d5-3cfa-75f7-af34-19f6171ae968_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_019c76d5-3cfa-75f7-af34-19f6171ae968" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019c76d5-3cfa-75f7-af34-19f6171ae968_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019c76d5-3cfa-7032-afde-06d74d30493f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_019c76d5-3cfa-75f7-af34-19f6171ae968" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019c76d5-3cfa-7032-afde-06d74d30493f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_ResidentialRealEstateExcludingAltAMember_019c76d5-3cfa-7b76-b280-d0010013f516" xlink:href="mtb-20260331.xsd#mtb_ResidentialRealEstateExcludingAltAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019c76d5-3cfa-7032-afde-06d74d30493f" xlink:to="loc_mtb_ResidentialRealEstateExcludingAltAMember_019c76d5-3cfa-7b76-b280-d0010013f516" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_HomeEquityLinesAndLoansMember_019c76d5-3cfa-70ff-a322-8fb4ff4b1ff2" xlink:href="mtb-20260331.xsd#mtb_HomeEquityLinesAndLoansMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019c76d5-3cfa-7032-afde-06d74d30493f" xlink:to="loc_mtb_HomeEquityLinesAndLoansMember_019c76d5-3cfa-70ff-a322-8fb4ff4b1ff2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_RecreationalFinanceMember_019c76d5-3cfa-78e2-9ce0-cd1366a4d603" xlink:href="mtb-20260331.xsd#mtb_RecreationalFinanceMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019c76d5-3cfa-7032-afde-06d74d30493f" xlink:to="loc_mtb_RecreationalFinanceMember_019c76d5-3cfa-78e2-9ce0-cd1366a4d603" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AutomobileLoanMember_019c76d5-3cfa-760f-96d5-b3f21516f6ff" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AutomobileLoanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019c76d5-3cfa-7032-afde-06d74d30493f" xlink:to="loc_us-gaap_AutomobileLoanMember_019c76d5-3cfa-760f-96d5-b3f21516f6ff" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_OtherLoansMember_019c76d5-3cfa-705e-9589-28e540848c39" xlink:href="mtb-20260331.xsd#mtb_OtherLoansMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019c76d5-3cfa-7032-afde-06d74d30493f" xlink:to="loc_mtb_OtherLoansMember_019c76d5-3cfa-705e-9589-28e540848c39" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityAxis_019c76d5-3cfa-7bae-9030-8ce1fdba26f4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CreditFacilityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFinancingReceivableRecordedInvestmentCreditQualityIndicatorTable_019c76d5-3cfa-71fc-a963-f0dda61bb3d6" xlink:to="loc_us-gaap_CreditFacilityAxis_019c76d5-3cfa-7bae-9030-8ce1fdba26f4" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_019c76d5-3cfa-7bae-9030-8ce1fdba26f4_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CreditFacilityAxis_019c76d5-3cfa-7bae-9030-8ce1fdba26f4" xlink:to="loc_us-gaap_CreditFacilityDomain_019c76d5-3cfa-7bae-9030-8ce1fdba26f4_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_019c76d5-3cfa-7acd-afab-330184492779" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CreditFacilityAxis_019c76d5-3cfa-7bae-9030-8ce1fdba26f4" xlink:to="loc_us-gaap_CreditFacilityDomain_019c76d5-3cfa-7acd-afab-330184492779" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevolvingCreditFacilityMember_019c76d5-3cfa-7f03-9ec6-3b390e1ae2a4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RevolvingCreditFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_019c76d5-3cfa-7acd-afab-330184492779" xlink:to="loc_us-gaap_RevolvingCreditFacilityMember_019c76d5-3cfa-7f03-9ec6-3b390e1ae2a4" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_RevolvingLoansConvertedToTermLoansMember_019c76d5-3cfa-7e5b-ae87-47f559713459" xlink:href="mtb-20260331.xsd#mtb_RevolvingLoansConvertedToTermLoansMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_019c76d5-3cfa-7acd-afab-330184492779" xlink:to="loc_mtb_RevolvingLoansConvertedToTermLoansMember_019c76d5-3cfa-7e5b-ae87-47f559713459" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_019c76d5-3cfa-7d65-aee0-b3a2b5b4217d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivablePortfolioSegmentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFinancingReceivableRecordedInvestmentCreditQualityIndicatorTable_019c76d5-3cfa-71fc-a963-f0dda61bb3d6" xlink:to="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_019c76d5-3cfa-7d65-aee0-b3a2b5b4217d" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019c76d5-3cfa-7d65-aee0-b3a2b5b4217d_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivablePortfolioSegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_019c76d5-3cfa-7d65-aee0-b3a2b5b4217d" xlink:to="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019c76d5-3cfa-7d65-aee0-b3a2b5b4217d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019c76d5-3cfa-774f-8a3d-b0bfe56b9792" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivablePortfolioSegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_019c76d5-3cfa-7d65-aee0-b3a2b5b4217d" xlink:to="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019c76d5-3cfa-774f-8a3d-b0bfe56b9792" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ResidentialPortfolioSegmentMember_019c76d5-3cfa-7639-99a7-5608f75cbfc7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ResidentialPortfolioSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019c76d5-3cfa-774f-8a3d-b0bfe56b9792" xlink:to="loc_us-gaap_ResidentialPortfolioSegmentMember_019c76d5-3cfa-7639-99a7-5608f75cbfc7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConsumerPortfolioSegmentMember_019c76d5-3cfa-7531-8006-5597a01fdf26" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ConsumerPortfolioSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019c76d5-3cfa-774f-8a3d-b0bfe56b9792" xlink:to="loc_us-gaap_ConsumerPortfolioSegmentMember_019c76d5-3cfa-7531-8006-5597a01fdf26" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestYearOneOriginatedCurrentFiscalYear_019c76d5-3cfa-73af-ace3-8ad4a3489be1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestYearOneOriginatedCurrentFiscalYear"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentLineItems_019c76d5-3cfa-7d28-9fe8-8b741d5f3924" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterestYearOneOriginatedCurrentFiscalYear_019c76d5-3cfa-73af-ace3-8ad4a3489be1" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestYearTwoOriginatedFiscalYearBeforeCurrentFiscalYear_019c76d5-3cfa-72ab-a442-dc56d66444a1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestYearTwoOriginatedFiscalYearBeforeCurrentFiscalYear"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentLineItems_019c76d5-3cfa-7d28-9fe8-8b741d5f3924" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterestYearTwoOriginatedFiscalYearBeforeCurrentFiscalYear_019c76d5-3cfa-72ab-a442-dc56d66444a1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestYearThreeOriginatedTwoYearsBeforeCurrentFiscalYear_019c76d5-3cfa-725e-bebf-e3dbcbaf2ad3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestYearThreeOriginatedTwoYearsBeforeCurrentFiscalYear"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentLineItems_019c76d5-3cfa-7d28-9fe8-8b741d5f3924" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterestYearThreeOriginatedTwoYearsBeforeCurrentFiscalYear_019c76d5-3cfa-725e-bebf-e3dbcbaf2ad3" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestYearFourOriginatedThreeYearsBeforeCurrentFiscalYear_019c76d5-3cfa-7104-a70a-a1b8b2374abe" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestYearFourOriginatedThreeYearsBeforeCurrentFiscalYear"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentLineItems_019c76d5-3cfa-7d28-9fe8-8b741d5f3924" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterestYearFourOriginatedThreeYearsBeforeCurrentFiscalYear_019c76d5-3cfa-7104-a70a-a1b8b2374abe" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestYearFiveOriginatedFourYearsBeforeCurrentFiscalYear_019c76d5-3cfa-7d0d-894f-28090f94055c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestYearFiveOriginatedFourYearsBeforeCurrentFiscalYear"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentLineItems_019c76d5-3cfa-7d28-9fe8-8b741d5f3924" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterestYearFiveOriginatedFourYearsBeforeCurrentFiscalYear_019c76d5-3cfa-7d0d-894f-28090f94055c" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestOriginatedMoreThanFiveYearsBeforeCurrentFiscalYear_019c76d5-3cfa-7518-af84-ebd8b085c686" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestOriginatedMoreThanFiveYearsBeforeCurrentFiscalYear"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentLineItems_019c76d5-3cfa-7d28-9fe8-8b741d5f3924" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterestOriginatedMoreThanFiveYearsBeforeCurrentFiscalYear_019c76d5-3cfa-7518-af84-ebd8b085c686" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestRevolving_019c76d5-3cfa-785a-96d3-c841515993c5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestRevolving"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentLineItems_019c76d5-3cfa-7d28-9fe8-8b741d5f3924" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterestRevolving_019c76d5-3cfa-785a-96d3-c841515993c5" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestRevolvingConvertedToTermLoan_019c76d5-3cfa-7777-965d-6d2a5c897cf6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestRevolvingConvertedToTermLoan"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentLineItems_019c76d5-3cfa-7d28-9fe8-8b741d5f3924" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterestRevolvingConvertedToTermLoan_019c76d5-3cfa-7777-965d-6d2a5c897cf6" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestBeforeAllowanceForCreditLossFeeAndLoanInProcess_019c76d5-3cfa-755e-8ca6-3f3c7441d521" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestBeforeAllowanceForCreditLossFeeAndLoanInProcess"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentLineItems_019c76d5-3cfa-7d28-9fe8-8b741d5f3924" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterestBeforeAllowanceForCreditLossFeeAndLoanInProcess_019c76d5-3cfa-755e-8ca6-3f3c7441d521" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestAllowanceForCreditLossWriteoffByOriginationYearAbstract_019c76d5-3cfa-7b81-91ad-ef9b1dcebb54" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestAllowanceForCreditLossWriteoffByOriginationYearAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentLineItems_019c76d5-3cfa-7d28-9fe8-8b741d5f3924" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterestAllowanceForCreditLossWriteoffByOriginationYearAbstract_019c76d5-3cfa-7b81-91ad-ef9b1dcebb54" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestYearOneOriginatedCurrentFiscalYearWriteoff_019c76d5-3cfa-76bc-bd40-7512c6eafde2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestYearOneOriginatedCurrentFiscalYearWriteoff"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableExcludingAccruedInterestAllowanceForCreditLossWriteoffByOriginationYearAbstract_019c76d5-3cfa-7b81-91ad-ef9b1dcebb54" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterestYearOneOriginatedCurrentFiscalYearWriteoff_019c76d5-3cfa-76bc-bd40-7512c6eafde2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestYearTwoOriginatedFiscalYearBeforeCurrentFiscalYearWriteoff_019c76d5-3cfa-72c9-8867-78f065544314" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestYearTwoOriginatedFiscalYearBeforeCurrentFiscalYearWriteoff"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableExcludingAccruedInterestAllowanceForCreditLossWriteoffByOriginationYearAbstract_019c76d5-3cfa-7b81-91ad-ef9b1dcebb54" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterestYearTwoOriginatedFiscalYearBeforeCurrentFiscalYearWriteoff_019c76d5-3cfa-72c9-8867-78f065544314" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestYearThreeOriginatedTwoYearsBeforeCurrentFiscalYearWriteoff_019c76d5-3cfa-7601-ac93-eec4f7ce1e18" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestYearThreeOriginatedTwoYearsBeforeCurrentFiscalYearWriteoff"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableExcludingAccruedInterestAllowanceForCreditLossWriteoffByOriginationYearAbstract_019c76d5-3cfa-7b81-91ad-ef9b1dcebb54" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterestYearThreeOriginatedTwoYearsBeforeCurrentFiscalYearWriteoff_019c76d5-3cfa-7601-ac93-eec4f7ce1e18" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestYearFourOriginatedThreeYearsBeforeCurrentFiscalYearWriteoff_019c76d5-3cfa-75a7-aa1d-5814ed2d1885" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestYearFourOriginatedThreeYearsBeforeCurrentFiscalYearWriteoff"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableExcludingAccruedInterestAllowanceForCreditLossWriteoffByOriginationYearAbstract_019c76d5-3cfa-7b81-91ad-ef9b1dcebb54" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterestYearFourOriginatedThreeYearsBeforeCurrentFiscalYearWriteoff_019c76d5-3cfa-75a7-aa1d-5814ed2d1885" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestYearFiveOriginatedFourYearsBeforeCurrentFiscalYearWriteoff_019c76d5-3cfa-7f1f-bb7c-36277a308cbf" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestYearFiveOriginatedFourYearsBeforeCurrentFiscalYearWriteoff"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableExcludingAccruedInterestAllowanceForCreditLossWriteoffByOriginationYearAbstract_019c76d5-3cfa-7b81-91ad-ef9b1dcebb54" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterestYearFiveOriginatedFourYearsBeforeCurrentFiscalYearWriteoff_019c76d5-3cfa-7f1f-bb7c-36277a308cbf" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestOriginatedMoreThanFiveYearsBeforeCurrentFiscalYearWriteoff_019c76d5-3cfa-71d2-85a9-26a5d0a0bd18" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestOriginatedMoreThanFiveYearsBeforeCurrentFiscalYearWriteoff"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableExcludingAccruedInterestAllowanceForCreditLossWriteoffByOriginationYearAbstract_019c76d5-3cfa-7b81-91ad-ef9b1dcebb54" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterestOriginatedMoreThanFiveYearsBeforeCurrentFiscalYearWriteoff_019c76d5-3cfa-71d2-85a9-26a5d0a0bd18" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestRevolvingWriteoff_019c76d5-3cfa-7c7d-b8b6-295ae55da460" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestRevolvingWriteoff"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableExcludingAccruedInterestAllowanceForCreditLossWriteoffByOriginationYearAbstract_019c76d5-3cfa-7b81-91ad-ef9b1dcebb54" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterestRevolvingWriteoff_019c76d5-3cfa-7c7d-b8b6-295ae55da460" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestRevolvingConvertedToTermLoanWriteoff_019c76d5-3cfa-788b-b561-a35549517691" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestRevolvingConvertedToTermLoanWriteoff"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableExcludingAccruedInterestAllowanceForCreditLossWriteoffByOriginationYearAbstract_019c76d5-3cfa-7b81-91ad-ef9b1dcebb54" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterestRevolvingConvertedToTermLoanWriteoff_019c76d5-3cfa-788b-b561-a35549517691" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestAllowanceForCreditLossWriteoff_019c76d5-3cfa-7714-9819-485b2777e580" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestAllowanceForCreditLossWriteoff"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableExcludingAccruedInterestAllowanceForCreditLossWriteoffByOriginationYearAbstract_019c76d5-3cfa-7b81-91ad-ef9b1dcebb54" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterestAllowanceForCreditLossWriteoff_019c76d5-3cfa-7714-9819-485b2777e580" xlink:type="arc" order="9"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.mtb.com/role/LoansandallowanceforloanlossesChangesinAllowanceforCreditLossesDetail" xlink:type="simple" xlink:href="mtb-20260331.xsd#LoansandallowanceforloanlossesChangesinAllowanceforCreditLossesDetail"/>
  <link:definitionLink xlink:role="http://www.mtb.com/role/LoansandallowanceforloanlossesChangesinAllowanceforCreditLossesDetail" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableAllowanceForCreditLossesLineItems_019c76d5-3cfa-79a5-b6f2-d77c1cbe38a8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableAllowanceForCreditLossesLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfFinancingReceivableAllowanceForCreditLossesTable_019c76d5-3cfa-76ca-be67-313c824bc584" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfFinancingReceivableAllowanceForCreditLossesTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FinancingReceivableAllowanceForCreditLossesLineItems_019c76d5-3cfa-79a5-b6f2-d77c1cbe38a8" xlink:to="loc_us-gaap_ScheduleOfFinancingReceivableAllowanceForCreditLossesTable_019c76d5-3cfa-76ca-be67-313c824bc584" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_019c76d5-3cfa-790f-8d27-94dd3c111a82" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivablePortfolioSegmentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFinancingReceivableAllowanceForCreditLossesTable_019c76d5-3cfa-76ca-be67-313c824bc584" xlink:to="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_019c76d5-3cfa-790f-8d27-94dd3c111a82" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019c76d5-3cfa-790f-8d27-94dd3c111a82_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivablePortfolioSegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_019c76d5-3cfa-790f-8d27-94dd3c111a82" xlink:to="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019c76d5-3cfa-790f-8d27-94dd3c111a82_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019c76d5-3cfa-7877-8f75-09643d288cda" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivablePortfolioSegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_019c76d5-3cfa-790f-8d27-94dd3c111a82" xlink:to="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019c76d5-3cfa-7877-8f75-09643d288cda" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_CommercialFinancialLeasingMember_019c76d5-3cfa-7064-b02a-aaeb2bfb7781" xlink:href="mtb-20260331.xsd#mtb_CommercialFinancialLeasingMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019c76d5-3cfa-7877-8f75-09643d288cda" xlink:to="loc_mtb_CommercialFinancialLeasingMember_019c76d5-3cfa-7064-b02a-aaeb2bfb7781" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommercialRealEstatePortfolioSegmentMember_019c76d5-3cfa-71f7-9983-4ce9b0c0ef78" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommercialRealEstatePortfolioSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019c76d5-3cfa-7877-8f75-09643d288cda" xlink:to="loc_us-gaap_CommercialRealEstatePortfolioSegmentMember_019c76d5-3cfa-71f7-9983-4ce9b0c0ef78" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ResidentialPortfolioSegmentMember_019c76d5-3cfa-792f-af87-6fdbafd44829" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ResidentialPortfolioSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019c76d5-3cfa-7877-8f75-09643d288cda" xlink:to="loc_us-gaap_ResidentialPortfolioSegmentMember_019c76d5-3cfa-792f-af87-6fdbafd44829" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConsumerPortfolioSegmentMember_019c76d5-3cfa-72fc-9d04-2263b7618c25" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ConsumerPortfolioSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019c76d5-3cfa-7877-8f75-09643d288cda" xlink:to="loc_us-gaap_ConsumerPortfolioSegmentMember_019c76d5-3cfa-72fc-9d04-2263b7618c25" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_ReserveForUnfundedCreditCommitmentsMember_019c76d5-3cfa-71d5-a463-3b8d0aa74155" xlink:href="mtb-20260331.xsd#mtb_ReserveForUnfundedCreditCommitmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019c76d5-3cfa-7877-8f75-09643d288cda" xlink:to="loc_mtb_ReserveForUnfundedCreditCommitmentsMember_019c76d5-3cfa-71d5-a463-3b8d0aa74155" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AllowanceForDoubtfulAccountsReceivableRollforward_019c76d5-3cfa-73a4-adf7-3f02fda8f95a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AllowanceForDoubtfulAccountsReceivableRollforward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableAllowanceForCreditLossesLineItems_019c76d5-3cfa-79a5-b6f2-d77c1cbe38a8" xlink:to="loc_us-gaap_AllowanceForDoubtfulAccountsReceivableRollforward_019c76d5-3cfa-73a4-adf7-3f02fda8f95a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableAllowanceForCreditLossExcludingAccruedInterest_019c76d5-3cfa-77fb-a65f-0514f48b7da4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableAllowanceForCreditLossExcludingAccruedInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AllowanceForDoubtfulAccountsReceivableRollforward_019c76d5-3cfa-73a4-adf7-3f02fda8f95a" xlink:to="loc_us-gaap_FinancingReceivableAllowanceForCreditLossExcludingAccruedInterest_019c76d5-3cfa-77fb-a65f-0514f48b7da4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestCreditLossExpenseReversal_019c76d5-3cfa-73db-953b-b66308b5a083" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestCreditLossExpenseReversal"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AllowanceForDoubtfulAccountsReceivableRollforward_019c76d5-3cfa-73a4-adf7-3f02fda8f95a" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterestCreditLossExpenseReversal_019c76d5-3cfa-73db-953b-b66308b5a083" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestAllowanceForCreditLossWriteoff_019c76d5-3cfa-7cde-8df9-c6da6e0235b0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestAllowanceForCreditLossWriteoff"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AllowanceForDoubtfulAccountsReceivableRollforward_019c76d5-3cfa-73a4-adf7-3f02fda8f95a" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterestAllowanceForCreditLossWriteoff_019c76d5-3cfa-7cde-8df9-c6da6e0235b0" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestAllowanceForCreditLossRecovery_019c76d5-3cfa-71fd-b86e-6c1faf39983c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestAllowanceForCreditLossRecovery"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AllowanceForDoubtfulAccountsReceivableRollforward_019c76d5-3cfa-73a4-adf7-3f02fda8f95a" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterestAllowanceForCreditLossRecovery_019c76d5-3cfa-71fd-b86e-6c1faf39983c" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestAllowanceForCreditLossWriteoffAfterRecovery_019c76d5-3cfa-76bc-8b30-90c372ce23ae" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestAllowanceForCreditLossWriteoffAfterRecovery"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AllowanceForDoubtfulAccountsReceivableRollforward_019c76d5-3cfa-73a4-adf7-3f02fda8f95a" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterestAllowanceForCreditLossWriteoffAfterRecovery_019c76d5-3cfa-76bc-8b30-90c372ce23ae" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableAllowanceForCreditLossExcludingAccruedInterest_019c76d5-3cfa-7a05-9487-1544c164a3b8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableAllowanceForCreditLossExcludingAccruedInterest"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.mtb.com/role/LoansandallowanceforloanlossesLoanandLeasesConsideredNonaccrualandInterestIncomeRecognizedonLoansDetail" xlink:type="simple" xlink:href="mtb-20260331.xsd#LoansandallowanceforloanlossesLoanandLeasesConsideredNonaccrualandInterestIncomeRecognizedonLoansDetail"/>
  <link:definitionLink xlink:role="http://www.mtb.com/role/LoansandallowanceforloanlossesLoanandLeasesConsideredNonaccrualandInterestIncomeRecognizedonLoansDetail" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableImpairedLineItems_019c76d5-3cfa-7674-ad88-a784efc7e16e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableImpairedLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfImpairedFinancingReceivableTable_019c76d5-3cfa-7376-a1a1-98d2bf6df4c4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfImpairedFinancingReceivableTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FinancingReceivableImpairedLineItems_019c76d5-3cfa-7674-ad88-a784efc7e16e" xlink:to="loc_us-gaap_ScheduleOfImpairedFinancingReceivableTable_019c76d5-3cfa-7376-a1a1-98d2bf6df4c4" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_019c76d5-3cfa-7fc6-a022-99a1d164cbfc" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivablePortfolioSegmentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfImpairedFinancingReceivableTable_019c76d5-3cfa-7376-a1a1-98d2bf6df4c4" xlink:to="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_019c76d5-3cfa-7fc6-a022-99a1d164cbfc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019c76d5-3cfa-7fc6-a022-99a1d164cbfc_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivablePortfolioSegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_019c76d5-3cfa-7fc6-a022-99a1d164cbfc" xlink:to="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019c76d5-3cfa-7fc6-a022-99a1d164cbfc_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019c76d5-3cfa-77d2-a493-a3d4f9848a7d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivablePortfolioSegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_019c76d5-3cfa-7fc6-a022-99a1d164cbfc" xlink:to="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019c76d5-3cfa-77d2-a493-a3d4f9848a7d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommercialPortfolioSegmentMember_019c76d5-3cfa-7219-8148-ac2a06c0a9f7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommercialPortfolioSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019c76d5-3cfa-77d2-a493-a3d4f9848a7d" xlink:to="loc_us-gaap_CommercialPortfolioSegmentMember_019c76d5-3cfa-7219-8148-ac2a06c0a9f7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommercialRealEstatePortfolioSegmentMember_019c76d5-3cfa-72e5-be63-a44049a9d666" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommercialRealEstatePortfolioSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019c76d5-3cfa-77d2-a493-a3d4f9848a7d" xlink:to="loc_us-gaap_CommercialRealEstatePortfolioSegmentMember_019c76d5-3cfa-72e5-be63-a44049a9d666" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ResidentialPortfolioSegmentMember_019c76d5-3cfa-7378-b1f9-b96f0911ab0e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ResidentialPortfolioSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019c76d5-3cfa-77d2-a493-a3d4f9848a7d" xlink:to="loc_us-gaap_ResidentialPortfolioSegmentMember_019c76d5-3cfa-7378-b1f9-b96f0911ab0e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConsumerPortfolioSegmentMember_019c76d5-3cfa-7c41-b5c8-6eb718a98145" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ConsumerPortfolioSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019c76d5-3cfa-77d2-a493-a3d4f9848a7d" xlink:to="loc_us-gaap_ConsumerPortfolioSegmentMember_019c76d5-3cfa-7c41-b5c8-6eb718a98145" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_019c76d5-3cfa-7964-85f1-487512a962e4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfImpairedFinancingReceivableTable_019c76d5-3cfa-7376-a1a1-98d2bf6df4c4" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_019c76d5-3cfa-7964-85f1-487512a962e4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019c76d5-3cfa-7964-85f1-487512a962e4_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_019c76d5-3cfa-7964-85f1-487512a962e4" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019c76d5-3cfa-7964-85f1-487512a962e4_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019c76d5-3cfa-7f12-93ed-659eb36cd980" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_019c76d5-3cfa-7964-85f1-487512a962e4" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019c76d5-3cfa-7f12-93ed-659eb36cd980" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_CommercialRealEstateExcludingResidentialBuilderAndDeveloperAndOtherConstructionMember_019c76d5-3cfa-7955-957f-97c1f1e511f3" xlink:href="mtb-20260331.xsd#mtb_CommercialRealEstateExcludingResidentialBuilderAndDeveloperAndOtherConstructionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019c76d5-3cfa-7f12-93ed-659eb36cd980" xlink:to="loc_mtb_CommercialRealEstateExcludingResidentialBuilderAndDeveloperAndOtherConstructionMember_019c76d5-3cfa-7955-957f-97c1f1e511f3" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_ResidentialBuilderAndDeveloperMember_019c76d5-3cfa-7f23-94b6-02300c798aba" xlink:href="mtb-20260331.xsd#mtb_ResidentialBuilderAndDeveloperMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019c76d5-3cfa-7f12-93ed-659eb36cd980" xlink:to="loc_mtb_ResidentialBuilderAndDeveloperMember_019c76d5-3cfa-7f23-94b6-02300c798aba" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_OtherCommercialConstructionMember_019c76d5-3cfa-73cb-bb12-529ad1a35492" xlink:href="mtb-20260331.xsd#mtb_OtherCommercialConstructionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019c76d5-3cfa-7f12-93ed-659eb36cd980" xlink:to="loc_mtb_OtherCommercialConstructionMember_019c76d5-3cfa-73cb-bb12-529ad1a35492" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_ResidentialRealEstateExcludingAltAMember_019c76d5-3cfa-739a-947e-0ea817c1320f" xlink:href="mtb-20260331.xsd#mtb_ResidentialRealEstateExcludingAltAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019c76d5-3cfa-7f12-93ed-659eb36cd980" xlink:to="loc_mtb_ResidentialRealEstateExcludingAltAMember_019c76d5-3cfa-739a-947e-0ea817c1320f" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_HomeEquityLinesAndLoansMember_019c76d5-3cfa-7443-8f7f-b357e1834711" xlink:href="mtb-20260331.xsd#mtb_HomeEquityLinesAndLoansMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019c76d5-3cfa-7f12-93ed-659eb36cd980" xlink:to="loc_mtb_HomeEquityLinesAndLoansMember_019c76d5-3cfa-7443-8f7f-b357e1834711" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_RecreationalFinanceMember_019c76d5-3cfa-79cc-b7d8-1bbf426d700a" xlink:href="mtb-20260331.xsd#mtb_RecreationalFinanceMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019c76d5-3cfa-7f12-93ed-659eb36cd980" xlink:to="loc_mtb_RecreationalFinanceMember_019c76d5-3cfa-79cc-b7d8-1bbf426d700a" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AutomobileLoanMember_019c76d5-3cfa-72e7-884f-98ebe58aa740" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AutomobileLoanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019c76d5-3cfa-7f12-93ed-659eb36cd980" xlink:to="loc_us-gaap_AutomobileLoanMember_019c76d5-3cfa-72e7-884f-98ebe58aa740" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConsumerOtherMember_019c76d5-3cfa-780d-9ba8-cfefe40af4de" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ConsumerOtherMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019c76d5-3cfa-7f12-93ed-659eb36cd980" xlink:to="loc_us-gaap_ConsumerOtherMember_019c76d5-3cfa-780d-9ba8-cfefe40af4de" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_FinancingReceivableExcludingAccruedInterestNonaccrualWithAllowance_019c76d5-3cfa-7b4a-a3b4-2d4db85a1705" xlink:href="mtb-20260331.xsd#mtb_FinancingReceivableExcludingAccruedInterestNonaccrualWithAllowance"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableImpairedLineItems_019c76d5-3cfa-7674-ad88-a784efc7e16e" xlink:to="loc_mtb_FinancingReceivableExcludingAccruedInterestNonaccrualWithAllowance_019c76d5-3cfa-7b4a-a3b4-2d4db85a1705" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestNonaccrualNoAllowance_019c76d5-3cfa-7a2e-8951-419a8e97fb9c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestNonaccrualNoAllowance"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableImpairedLineItems_019c76d5-3cfa-7674-ad88-a784efc7e16e" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterestNonaccrualNoAllowance_019c76d5-3cfa-7a2e-8951-419a8e97fb9c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestNonaccrual_019c76d5-3cfa-7b15-8c90-ecd3cd3aadb5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestNonaccrual"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableImpairedLineItems_019c76d5-3cfa-7674-ad88-a784efc7e16e" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterestNonaccrual_019c76d5-3cfa-7b15-8c90-ecd3cd3aadb5" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestNonaccrual_019c76d5-3cfa-760d-afc5-9cf562fb7b36" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestNonaccrual"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_ImpairedFinancingReceivableNonaccrualInterestIncome_019c76d5-3cfa-7d35-9333-d2ca82a1634d" xlink:href="mtb-20260331.xsd#mtb_ImpairedFinancingReceivableNonaccrualInterestIncome"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableImpairedLineItems_019c76d5-3cfa-7674-ad88-a784efc7e16e" xlink:to="loc_mtb_ImpairedFinancingReceivableNonaccrualInterestIncome_019c76d5-3cfa-7d35-9333-d2ca82a1634d" xlink:type="arc" order="4"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.mtb.com/role/LoansandallowanceforloanlossesLoanModificationActivitiestoBorrowersExperiencingFinancialDifficultyonFinancingReceivablesDetail" xlink:type="simple" xlink:href="mtb-20260331.xsd#LoansandallowanceforloanlossesLoanModificationActivitiestoBorrowersExperiencingFinancialDifficultyonFinancingReceivablesDetail"/>
  <link:definitionLink xlink:role="http://www.mtb.com/role/LoansandallowanceforloanlossesLoanModificationActivitiestoBorrowersExperiencingFinancialDifficultyonFinancingReceivablesDetail" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_mtb_FinancingReceivableModificationsOtherThanTroubledDebtRestructuringLineItems_019c76d5-3cfa-7bd2-b6ba-251b6292cb6d" xlink:href="mtb-20260331.xsd#mtb_FinancingReceivableModificationsOtherThanTroubledDebtRestructuringLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfFinancingReceivableTroubledDebtRestructuringsTable_019c76d5-3cfa-7658-9378-d20965d59ce3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfFinancingReceivableTroubledDebtRestructuringsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_mtb_FinancingReceivableModificationsOtherThanTroubledDebtRestructuringLineItems_019c76d5-3cfa-7bd2-b6ba-251b6292cb6d" xlink:to="loc_us-gaap_ScheduleOfFinancingReceivableTroubledDebtRestructuringsTable_019c76d5-3cfa-7658-9378-d20965d59ce3" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LoanRestructuringModificationAxis_019c76d5-3cfa-7a6e-8be4-bd6821fd9d06" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LoanRestructuringModificationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFinancingReceivableTroubledDebtRestructuringsTable_019c76d5-3cfa-7658-9378-d20965d59ce3" xlink:to="loc_us-gaap_LoanRestructuringModificationAxis_019c76d5-3cfa-7a6e-8be4-bd6821fd9d06" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LoanRestructuringModificationDomain_019c76d5-3cfa-7a6e-8be4-bd6821fd9d06_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LoanRestructuringModificationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LoanRestructuringModificationAxis_019c76d5-3cfa-7a6e-8be4-bd6821fd9d06" xlink:to="loc_us-gaap_LoanRestructuringModificationDomain_019c76d5-3cfa-7a6e-8be4-bd6821fd9d06_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LoanRestructuringModificationDomain_019c76d5-3cfa-75b3-9988-f3f90dc87350" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LoanRestructuringModificationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LoanRestructuringModificationAxis_019c76d5-3cfa-7a6e-8be4-bd6821fd9d06" xlink:to="loc_us-gaap_LoanRestructuringModificationDomain_019c76d5-3cfa-75b3-9988-f3f90dc87350" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentDeferralMember_019c76d5-3cfa-7606-b88b-72641df30d13" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PaymentDeferralMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LoanRestructuringModificationDomain_019c76d5-3cfa-75b3-9988-f3f90dc87350" xlink:to="loc_us-gaap_PaymentDeferralMember_019c76d5-3cfa-7606-b88b-72641df30d13" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractualInterestRateReductionMember_019c76d5-3cfa-7ed9-b8b5-1c5745b1262e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ContractualInterestRateReductionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LoanRestructuringModificationDomain_019c76d5-3cfa-75b3-9988-f3f90dc87350" xlink:to="loc_us-gaap_ContractualInterestRateReductionMember_019c76d5-3cfa-7ed9-b8b5-1c5745b1262e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_CombinationOfModificationTypesMember_019c76d5-3cfa-7b87-9954-5154d12a7f3f" xlink:href="mtb-20260331.xsd#mtb_CombinationOfModificationTypesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LoanRestructuringModificationDomain_019c76d5-3cfa-75b3-9988-f3f90dc87350" xlink:to="loc_mtb_CombinationOfModificationTypesMember_019c76d5-3cfa-7b87-9954-5154d12a7f3f" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_019c76d5-3cfa-7c19-8d74-adff445805ce" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFinancingReceivableTroubledDebtRestructuringsTable_019c76d5-3cfa-7658-9378-d20965d59ce3" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_019c76d5-3cfa-7c19-8d74-adff445805ce" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019c76d5-3cfa-7c19-8d74-adff445805ce_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_019c76d5-3cfa-7c19-8d74-adff445805ce" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019c76d5-3cfa-7c19-8d74-adff445805ce_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019c76d5-3cfa-7e3a-86e0-461ac8fca419" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_019c76d5-3cfa-7c19-8d74-adff445805ce" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019c76d5-3cfa-7e3a-86e0-461ac8fca419" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_CommercialRealEstateExcludingResidentialBuilderAndDeveloperAndOtherConstructionMember_019c76d5-3cfa-724a-8c21-f04b8311f5e6" xlink:href="mtb-20260331.xsd#mtb_CommercialRealEstateExcludingResidentialBuilderAndDeveloperAndOtherConstructionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019c76d5-3cfa-7e3a-86e0-461ac8fca419" xlink:to="loc_mtb_CommercialRealEstateExcludingResidentialBuilderAndDeveloperAndOtherConstructionMember_019c76d5-3cfa-724a-8c21-f04b8311f5e6" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_ResidentialBuilderAndDeveloperMember_019c76d5-3cfa-7d5b-ad74-c03c0ea68562" xlink:href="mtb-20260331.xsd#mtb_ResidentialBuilderAndDeveloperMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019c76d5-3cfa-7e3a-86e0-461ac8fca419" xlink:to="loc_mtb_ResidentialBuilderAndDeveloperMember_019c76d5-3cfa-7d5b-ad74-c03c0ea68562" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_OtherCommercialConstructionMember_019c76d5-3cfa-7c68-a997-1b9275a41bb5" xlink:href="mtb-20260331.xsd#mtb_OtherCommercialConstructionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019c76d5-3cfa-7e3a-86e0-461ac8fca419" xlink:to="loc_mtb_OtherCommercialConstructionMember_019c76d5-3cfa-7c68-a997-1b9275a41bb5" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_ResidentialRealEstateExcludingAltAMember_019c76d5-3cfa-7bbb-8a89-586d65a05242" xlink:href="mtb-20260331.xsd#mtb_ResidentialRealEstateExcludingAltAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019c76d5-3cfa-7e3a-86e0-461ac8fca419" xlink:to="loc_mtb_ResidentialRealEstateExcludingAltAMember_019c76d5-3cfa-7bbb-8a89-586d65a05242" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_HomeEquityLinesAndLoansMember_019c76d5-3cfa-7f6f-b31e-90ebaec1e79b" xlink:href="mtb-20260331.xsd#mtb_HomeEquityLinesAndLoansMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019c76d5-3cfa-7e3a-86e0-461ac8fca419" xlink:to="loc_mtb_HomeEquityLinesAndLoansMember_019c76d5-3cfa-7f6f-b31e-90ebaec1e79b" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_RecreationalFinanceMember_019c76d5-3cfa-79af-9dd3-d43954a68a8d" xlink:href="mtb-20260331.xsd#mtb_RecreationalFinanceMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019c76d5-3cfa-7e3a-86e0-461ac8fca419" xlink:to="loc_mtb_RecreationalFinanceMember_019c76d5-3cfa-79af-9dd3-d43954a68a8d" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AutomobileLoanMember_019c76d5-3cfa-77db-aa9a-5fbfa10ee03f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AutomobileLoanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019c76d5-3cfa-7e3a-86e0-461ac8fca419" xlink:to="loc_us-gaap_AutomobileLoanMember_019c76d5-3cfa-77db-aa9a-5fbfa10ee03f" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConsumerOtherMember_019c76d5-3cfa-7921-b257-f664708e6eff" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ConsumerOtherMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019c76d5-3cfa-7e3a-86e0-461ac8fca419" xlink:to="loc_us-gaap_ConsumerOtherMember_019c76d5-3cfa-7921-b257-f664708e6eff" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnfundedLoanCommitmentMember_019c76d5-3cfa-75ca-8b40-5dab87178ea5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_UnfundedLoanCommitmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019c76d5-3cfa-7e3a-86e0-461ac8fca419" xlink:to="loc_us-gaap_UnfundedLoanCommitmentMember_019c76d5-3cfa-75ca-8b40-5dab87178ea5" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_019c76d5-3cfa-7470-8bbd-1eee33707f42" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivablePortfolioSegmentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFinancingReceivableTroubledDebtRestructuringsTable_019c76d5-3cfa-7658-9378-d20965d59ce3" xlink:to="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_019c76d5-3cfa-7470-8bbd-1eee33707f42" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019c76d5-3cfa-7470-8bbd-1eee33707f42_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivablePortfolioSegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_019c76d5-3cfa-7470-8bbd-1eee33707f42" xlink:to="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019c76d5-3cfa-7470-8bbd-1eee33707f42_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019c76d5-3cfa-7f55-b3d7-a3ab869e35e5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivablePortfolioSegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_019c76d5-3cfa-7470-8bbd-1eee33707f42" xlink:to="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019c76d5-3cfa-7f55-b3d7-a3ab869e35e5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommercialPortfolioSegmentMember_019c76d5-3cfa-7cf4-914e-189cd255de54" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommercialPortfolioSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019c76d5-3cfa-7f55-b3d7-a3ab869e35e5" xlink:to="loc_us-gaap_CommercialPortfolioSegmentMember_019c76d5-3cfa-7cf4-914e-189cd255de54" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommercialRealEstatePortfolioSegmentMember_019c76d5-3cfa-7d9e-999a-9381ac2750b7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommercialRealEstatePortfolioSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019c76d5-3cfa-7f55-b3d7-a3ab869e35e5" xlink:to="loc_us-gaap_CommercialRealEstatePortfolioSegmentMember_019c76d5-3cfa-7d9e-999a-9381ac2750b7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ResidentialPortfolioSegmentMember_019c76d5-3cfa-76eb-968a-e6b4ac9a0fc7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ResidentialPortfolioSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019c76d5-3cfa-7f55-b3d7-a3ab869e35e5" xlink:to="loc_us-gaap_ResidentialPortfolioSegmentMember_019c76d5-3cfa-76eb-968a-e6b4ac9a0fc7" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConsumerPortfolioSegmentMember_019c76d5-3cfa-75d3-9e76-13c68e5dc8f3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ConsumerPortfolioSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019c76d5-3cfa-7f55-b3d7-a3ab869e35e5" xlink:to="loc_us-gaap_ConsumerPortfolioSegmentMember_019c76d5-3cfa-75d3-9e76-13c68e5dc8f3" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LoansInsuredOrGuaranteedByGovernmentAuthoritiesAxis_019c76d5-3cfa-7cc3-a373-555f3a5e7528" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LoansInsuredOrGuaranteedByGovernmentAuthoritiesAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFinancingReceivableTroubledDebtRestructuringsTable_019c76d5-3cfa-7658-9378-d20965d59ce3" xlink:to="loc_us-gaap_LoansInsuredOrGuaranteedByGovernmentAuthoritiesAxis_019c76d5-3cfa-7cc3-a373-555f3a5e7528" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LoansInsuredOrGuaranteedByGovernmentAuthoritiesDomain_019c76d5-3cfa-7cc3-a373-555f3a5e7528_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LoansInsuredOrGuaranteedByGovernmentAuthoritiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LoansInsuredOrGuaranteedByGovernmentAuthoritiesAxis_019c76d5-3cfa-7cc3-a373-555f3a5e7528" xlink:to="loc_us-gaap_LoansInsuredOrGuaranteedByGovernmentAuthoritiesDomain_019c76d5-3cfa-7cc3-a373-555f3a5e7528_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LoansInsuredOrGuaranteedByGovernmentAuthoritiesDomain_019c76d5-3cfa-7f6c-805d-4537fa4671fe" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LoansInsuredOrGuaranteedByGovernmentAuthoritiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LoansInsuredOrGuaranteedByGovernmentAuthoritiesAxis_019c76d5-3cfa-7cc3-a373-555f3a5e7528" xlink:to="loc_us-gaap_LoansInsuredOrGuaranteedByGovernmentAuthoritiesDomain_019c76d5-3cfa-7f6c-805d-4537fa4671fe" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LoansInsuredOrGuaranteedByUsGovernmentAuthoritiesMember_019c76d5-3cfa-7eee-a2a4-c7824d690f86" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LoansInsuredOrGuaranteedByUsGovernmentAuthoritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LoansInsuredOrGuaranteedByGovernmentAuthoritiesDomain_019c76d5-3cfa-7f6c-805d-4537fa4671fe" xlink:to="loc_us-gaap_LoansInsuredOrGuaranteedByUsGovernmentAuthoritiesMember_019c76d5-3cfa-7eee-a2a4-c7824d690f86" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestModifiedPeriod_019c76d5-3cfa-7576-9ee8-d9bb24c5be37" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestModifiedPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_mtb_FinancingReceivableModificationsOtherThanTroubledDebtRestructuringLineItems_019c76d5-3cfa-7bd2-b6ba-251b6292cb6d" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterestModifiedPeriod_019c76d5-3cfa-7576-9ee8-d9bb24c5be37" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableModificationToTotalFinancingReceivablesExcludingAccruedInterestPercent_019c76d5-3cfa-7df2-aa13-b8658ad2fa98" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableModificationToTotalFinancingReceivablesExcludingAccruedInterestPercent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_mtb_FinancingReceivableModificationsOtherThanTroubledDebtRestructuringLineItems_019c76d5-3cfa-7bd2-b6ba-251b6292cb6d" xlink:to="loc_us-gaap_FinancingReceivableModificationToTotalFinancingReceivablesExcludingAccruedInterestPercent_019c76d5-3cfa-7df2-aa13-b8658ad2fa98" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.mtb.com/role/LoansandallowanceforloanlossesEffectofLoanModificationonWeightedaverageRemainingLifeDetail" xlink:type="simple" xlink:href="mtb-20260331.xsd#LoansandallowanceforloanlossesEffectofLoanModificationonWeightedaverageRemainingLifeDetail"/>
  <link:definitionLink xlink:role="http://www.mtb.com/role/LoansandallowanceforloanlossesEffectofLoanModificationonWeightedaverageRemainingLifeDetail" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableModificationsLineItems_019c76d5-3cfa-74fe-9f15-6ae5ff2a8aee" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableModificationsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfFinancingReceivableTroubledDebtRestructuringsTable_019c76d5-3cfa-7a37-8dd8-8264e3b58d54" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfFinancingReceivableTroubledDebtRestructuringsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FinancingReceivableModificationsLineItems_019c76d5-3cfa-74fe-9f15-6ae5ff2a8aee" xlink:to="loc_us-gaap_ScheduleOfFinancingReceivableTroubledDebtRestructuringsTable_019c76d5-3cfa-7a37-8dd8-8264e3b58d54" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_019c76d5-3cfa-72a8-a241-f038a1f61897" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivablePortfolioSegmentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFinancingReceivableTroubledDebtRestructuringsTable_019c76d5-3cfa-7a37-8dd8-8264e3b58d54" xlink:to="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_019c76d5-3cfa-72a8-a241-f038a1f61897" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019c76d5-3cfa-72a8-a241-f038a1f61897_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivablePortfolioSegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_019c76d5-3cfa-72a8-a241-f038a1f61897" xlink:to="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019c76d5-3cfa-72a8-a241-f038a1f61897_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019c76d5-3cfa-7a97-9f65-30c4cea16c16" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivablePortfolioSegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_019c76d5-3cfa-72a8-a241-f038a1f61897" xlink:to="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019c76d5-3cfa-7a97-9f65-30c4cea16c16" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommercialPortfolioSegmentMember_019c76d5-3cfa-76b3-a4d5-4c719eeccc83" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommercialPortfolioSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019c76d5-3cfa-7a97-9f65-30c4cea16c16" xlink:to="loc_us-gaap_CommercialPortfolioSegmentMember_019c76d5-3cfa-76b3-a4d5-4c719eeccc83" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommercialRealEstatePortfolioSegmentMember_019c76d5-3cfa-723e-acd7-0c4b46bf4ede" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommercialRealEstatePortfolioSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019c76d5-3cfa-7a97-9f65-30c4cea16c16" xlink:to="loc_us-gaap_CommercialRealEstatePortfolioSegmentMember_019c76d5-3cfa-723e-acd7-0c4b46bf4ede" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ResidentialPortfolioSegmentMember_019c76d5-3cfa-7e24-9f10-0b341f1b8653" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ResidentialPortfolioSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019c76d5-3cfa-7a97-9f65-30c4cea16c16" xlink:to="loc_us-gaap_ResidentialPortfolioSegmentMember_019c76d5-3cfa-7e24-9f10-0b341f1b8653" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_LoansAndLeasesWeightedAverageRemainingTerm_019c76d5-3cfa-75bb-8426-824c284fb6cc" xlink:href="mtb-20260331.xsd#mtb_LoansAndLeasesWeightedAverageRemainingTerm"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableModificationsLineItems_019c76d5-3cfa-74fe-9f15-6ae5ff2a8aee" xlink:to="loc_mtb_LoansAndLeasesWeightedAverageRemainingTerm_019c76d5-3cfa-75bb-8426-824c284fb6cc" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.mtb.com/role/LoansandallowanceforloanlossesSummaryofPaymentStatusofLoansModifiedDetail" xlink:type="simple" xlink:href="mtb-20260331.xsd#LoansandallowanceforloanlossesSummaryofPaymentStatusofLoansModifiedDetail"/>
  <link:definitionLink xlink:role="http://www.mtb.com/role/LoansandallowanceforloanlossesSummaryofPaymentStatusofLoansModifiedDetail" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsNotesAndLoansReceivableLineItems_019c76d5-3cfa-791e-ae54-05abe2f7157f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccountsNotesAndLoansReceivableLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfAccountsNotesLoansAndFinancingReceivableTable_019c76d5-3cfa-7ee8-bcf5-1492e6f9f892" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfAccountsNotesLoansAndFinancingReceivableTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_AccountsNotesAndLoansReceivableLineItems_019c76d5-3cfa-791e-ae54-05abe2f7157f" xlink:to="loc_us-gaap_ScheduleOfAccountsNotesLoansAndFinancingReceivableTable_019c76d5-3cfa-7ee8-bcf5-1492e6f9f892" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_019c76d5-3cfa-78fc-b6bc-aaf34684930a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivablePortfolioSegmentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfAccountsNotesLoansAndFinancingReceivableTable_019c76d5-3cfa-7ee8-bcf5-1492e6f9f892" xlink:to="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_019c76d5-3cfa-78fc-b6bc-aaf34684930a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019c76d5-3cfa-78fc-b6bc-aaf34684930a_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivablePortfolioSegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_019c76d5-3cfa-78fc-b6bc-aaf34684930a" xlink:to="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019c76d5-3cfa-78fc-b6bc-aaf34684930a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019c76d5-3cfa-7cb4-b513-f5c779df46ac" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivablePortfolioSegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_019c76d5-3cfa-78fc-b6bc-aaf34684930a" xlink:to="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019c76d5-3cfa-7cb4-b513-f5c779df46ac" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_CommercialFinancialLeasingMember_019c76d5-3cfa-7cde-b8ff-f0883fef2f0c" xlink:href="mtb-20260331.xsd#mtb_CommercialFinancialLeasingMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019c76d5-3cfa-7cb4-b513-f5c779df46ac" xlink:to="loc_mtb_CommercialFinancialLeasingMember_019c76d5-3cfa-7cde-b8ff-f0883fef2f0c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommercialRealEstatePortfolioSegmentMember_019c76d5-3cfa-7877-bd6b-23218505801f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommercialRealEstatePortfolioSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019c76d5-3cfa-7cb4-b513-f5c779df46ac" xlink:to="loc_us-gaap_CommercialRealEstatePortfolioSegmentMember_019c76d5-3cfa-7877-bd6b-23218505801f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ResidentialPortfolioSegmentMember_019c76d5-3cfa-7826-8be2-123078dccbbf" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ResidentialPortfolioSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019c76d5-3cfa-7cb4-b513-f5c779df46ac" xlink:to="loc_us-gaap_ResidentialPortfolioSegmentMember_019c76d5-3cfa-7826-8be2-123078dccbbf" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConsumerPortfolioSegmentMember_019c76d5-3cfa-78af-aa84-0517bfd932fa" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ConsumerPortfolioSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019c76d5-3cfa-7cb4-b513-f5c779df46ac" xlink:to="loc_us-gaap_ConsumerPortfolioSegmentMember_019c76d5-3cfa-78af-aa84-0517bfd932fa" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_019c76d5-3cfa-7cbe-9036-d9b74347233c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfAccountsNotesLoansAndFinancingReceivableTable_019c76d5-3cfa-7ee8-bcf5-1492e6f9f892" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_019c76d5-3cfa-7cbe-9036-d9b74347233c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019c76d5-3cfa-7cbe-9036-d9b74347233c_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_019c76d5-3cfa-7cbe-9036-d9b74347233c" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019c76d5-3cfa-7cbe-9036-d9b74347233c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019c76d5-3cfa-757d-ad3e-c2af3d47675a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_019c76d5-3cfa-7cbe-9036-d9b74347233c" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019c76d5-3cfa-757d-ad3e-c2af3d47675a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_CommercialRealEstateExcludingResidentialBuilderAndDeveloperAndOtherConstructionMember_019c76d5-3cfa-72d3-9630-4de90f257b8e" xlink:href="mtb-20260331.xsd#mtb_CommercialRealEstateExcludingResidentialBuilderAndDeveloperAndOtherConstructionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019c76d5-3cfa-757d-ad3e-c2af3d47675a" xlink:to="loc_mtb_CommercialRealEstateExcludingResidentialBuilderAndDeveloperAndOtherConstructionMember_019c76d5-3cfa-72d3-9630-4de90f257b8e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_ResidentialBuilderAndDeveloperMember_019c76d5-3cfa-7129-b9d0-f6ddcf6077f2" xlink:href="mtb-20260331.xsd#mtb_ResidentialBuilderAndDeveloperMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019c76d5-3cfa-757d-ad3e-c2af3d47675a" xlink:to="loc_mtb_ResidentialBuilderAndDeveloperMember_019c76d5-3cfa-7129-b9d0-f6ddcf6077f2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_OtherCommercialConstructionMember_019c76d5-3cfa-723f-9dfa-275be8ac82d3" xlink:href="mtb-20260331.xsd#mtb_OtherCommercialConstructionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019c76d5-3cfa-757d-ad3e-c2af3d47675a" xlink:to="loc_mtb_OtherCommercialConstructionMember_019c76d5-3cfa-723f-9dfa-275be8ac82d3" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_ResidentialRealEstateExcludingAltAMember_019c76d5-3cfa-7b47-846b-f5b303078d29" xlink:href="mtb-20260331.xsd#mtb_ResidentialRealEstateExcludingAltAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019c76d5-3cfa-757d-ad3e-c2af3d47675a" xlink:to="loc_mtb_ResidentialRealEstateExcludingAltAMember_019c76d5-3cfa-7b47-846b-f5b303078d29" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_HomeEquityLinesAndLoansMember_019c76d5-3cfa-7081-9c34-a879eb4f20ae" xlink:href="mtb-20260331.xsd#mtb_HomeEquityLinesAndLoansMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019c76d5-3cfa-757d-ad3e-c2af3d47675a" xlink:to="loc_mtb_HomeEquityLinesAndLoansMember_019c76d5-3cfa-7081-9c34-a879eb4f20ae" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_RecreationalFinanceMember_019c76d5-3cfa-752a-9220-54908d483836" xlink:href="mtb-20260331.xsd#mtb_RecreationalFinanceMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019c76d5-3cfa-757d-ad3e-c2af3d47675a" xlink:to="loc_mtb_RecreationalFinanceMember_019c76d5-3cfa-752a-9220-54908d483836" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AutomobileLoanMember_019c76d5-3cfa-7f7e-9858-7272b2758a8e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AutomobileLoanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019c76d5-3cfa-757d-ad3e-c2af3d47675a" xlink:to="loc_us-gaap_AutomobileLoanMember_019c76d5-3cfa-7f7e-9858-7272b2758a8e" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_OtherLoansMember_019c76d5-3cfa-72b4-833b-be93c2c0cf1e" xlink:href="mtb-20260331.xsd#mtb_OtherLoansMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019c76d5-3cfa-757d-ad3e-c2af3d47675a" xlink:to="loc_mtb_OtherLoansMember_019c76d5-3cfa-72b4-833b-be93c2c0cf1e" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivablesPeriodPastDueAxis_019c76d5-3cfa-72ce-93f0-441624c4704b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivablesPeriodPastDueAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfAccountsNotesLoansAndFinancingReceivableTable_019c76d5-3cfa-7ee8-bcf5-1492e6f9f892" xlink:to="loc_us-gaap_FinancingReceivablesPeriodPastDueAxis_019c76d5-3cfa-72ce-93f0-441624c4704b" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivablesPeriodPastDueDomain_019c76d5-3cfa-72ce-93f0-441624c4704b_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivablesPeriodPastDueDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancingReceivablesPeriodPastDueAxis_019c76d5-3cfa-72ce-93f0-441624c4704b" xlink:to="loc_us-gaap_FinancingReceivablesPeriodPastDueDomain_019c76d5-3cfa-72ce-93f0-441624c4704b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivablesPeriodPastDueDomain_019c76d5-3cfa-7a8d-ba58-d921412e6f5e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivablesPeriodPastDueDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancingReceivablesPeriodPastDueAxis_019c76d5-3cfa-72ce-93f0-441624c4704b" xlink:to="loc_us-gaap_FinancingReceivablesPeriodPastDueDomain_019c76d5-3cfa-7a8d-ba58-d921412e6f5e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialAssetNotPastDueMember_019c76d5-3cfa-78c8-9a26-877b30321170" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancialAssetNotPastDueMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivablesPeriodPastDueDomain_019c76d5-3cfa-7a8d-ba58-d921412e6f5e" xlink:to="loc_us-gaap_FinancialAssetNotPastDueMember_019c76d5-3cfa-78c8-9a26-877b30321170" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivables30To59DaysPastDueMember_019c76d5-3cfa-7714-aedf-d0f8d9bd25fb" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivables30To59DaysPastDueMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivablesPeriodPastDueDomain_019c76d5-3cfa-7a8d-ba58-d921412e6f5e" xlink:to="loc_us-gaap_FinancingReceivables30To59DaysPastDueMember_019c76d5-3cfa-7714-aedf-d0f8d9bd25fb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivablesEqualToGreaterThan90DaysPastDueMember_019c76d5-3cfa-7e5c-a220-e18bc7e5ff79" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivablesEqualToGreaterThan90DaysPastDueMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivablesPeriodPastDueDomain_019c76d5-3cfa-7a8d-ba58-d921412e6f5e" xlink:to="loc_us-gaap_FinancingReceivablesEqualToGreaterThan90DaysPastDueMember_019c76d5-3cfa-7e5c-a220-e18bc7e5ff79" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LoansInsuredOrGuaranteedByGovernmentAuthoritiesAxis_019c76d5-3cfa-757c-a1a0-ac6991ee1449" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LoansInsuredOrGuaranteedByGovernmentAuthoritiesAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfAccountsNotesLoansAndFinancingReceivableTable_019c76d5-3cfa-7ee8-bcf5-1492e6f9f892" xlink:to="loc_us-gaap_LoansInsuredOrGuaranteedByGovernmentAuthoritiesAxis_019c76d5-3cfa-757c-a1a0-ac6991ee1449" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LoansInsuredOrGuaranteedByGovernmentAuthoritiesDomain_019c76d5-3cfa-757c-a1a0-ac6991ee1449_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LoansInsuredOrGuaranteedByGovernmentAuthoritiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LoansInsuredOrGuaranteedByGovernmentAuthoritiesAxis_019c76d5-3cfa-757c-a1a0-ac6991ee1449" xlink:to="loc_us-gaap_LoansInsuredOrGuaranteedByGovernmentAuthoritiesDomain_019c76d5-3cfa-757c-a1a0-ac6991ee1449_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LoansInsuredOrGuaranteedByGovernmentAuthoritiesDomain_019c76d5-3cfa-7611-b73f-a861de7aa222" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LoansInsuredOrGuaranteedByGovernmentAuthoritiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LoansInsuredOrGuaranteedByGovernmentAuthoritiesAxis_019c76d5-3cfa-757c-a1a0-ac6991ee1449" xlink:to="loc_us-gaap_LoansInsuredOrGuaranteedByGovernmentAuthoritiesDomain_019c76d5-3cfa-7611-b73f-a861de7aa222" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LoansInsuredOrGuaranteedByUsGovernmentAuthoritiesMember_019c76d5-3cfa-71d9-b62b-ba9b3aa96d9f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LoansInsuredOrGuaranteedByUsGovernmentAuthoritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LoansInsuredOrGuaranteedByGovernmentAuthoritiesDomain_019c76d5-3cfa-7611-b73f-a861de7aa222" xlink:to="loc_us-gaap_LoansInsuredOrGuaranteedByUsGovernmentAuthoritiesMember_019c76d5-3cfa-71d9-b62b-ba9b3aa96d9f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestModifiedPast12Months_019c76d5-3cfa-74a3-a2f0-64097992d597" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestModifiedPast12Months"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccountsNotesAndLoansReceivableLineItems_019c76d5-3cfa-791e-ae54-05abe2f7157f" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterestModifiedPast12Months_019c76d5-3cfa-74a3-a2f0-64097992d597" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_DelinquencyStatusOfLoansAndLeasesReceivableModifiedPastDueThirtyToEightyNineDays_019c76d5-3cfa-79cb-ab05-dcdee9dc9cb4" xlink:href="mtb-20260331.xsd#mtb_DelinquencyStatusOfLoansAndLeasesReceivableModifiedPastDueThirtyToEightyNineDays"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccountsNotesAndLoansReceivableLineItems_019c76d5-3cfa-791e-ae54-05abe2f7157f" xlink:to="loc_mtb_DelinquencyStatusOfLoansAndLeasesReceivableModifiedPastDueThirtyToEightyNineDays_019c76d5-3cfa-79cb-ab05-dcdee9dc9cb4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_DelinquencyStatusOfLoansAndLeasesReceivableModifiedPastDueNinetyDaysOrMore_019c76d5-3cfa-7bb3-a697-badac07fe223" xlink:href="mtb-20260331.xsd#mtb_DelinquencyStatusOfLoansAndLeasesReceivableModifiedPastDueNinetyDaysOrMore"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccountsNotesAndLoansReceivableLineItems_019c76d5-3cfa-791e-ae54-05abe2f7157f" xlink:to="loc_mtb_DelinquencyStatusOfLoansAndLeasesReceivableModifiedPastDueNinetyDaysOrMore_019c76d5-3cfa-7bb3-a697-badac07fe223" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.mtb.com/role/BorrowingsScheduleofBorrowingsDetails" xlink:type="simple" xlink:href="mtb-20260331.xsd#BorrowingsScheduleofBorrowingsDetails"/>
  <link:definitionLink xlink:role="http://www.mtb.com/role/BorrowingsScheduleofBorrowingsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_mtb_ScheduleOfBorrowingsLineItems_019c76d5-3cfa-73b6-8369-f6c568538f2f" xlink:href="mtb-20260331.xsd#mtb_ScheduleOfBorrowingsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_ScheduleOfBorrowingsTable_019c76d5-3cfa-759a-9887-82da0c30320d" xlink:href="mtb-20260331.xsd#mtb_ScheduleOfBorrowingsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_mtb_ScheduleOfBorrowingsLineItems_019c76d5-3cfa-73b6-8369-f6c568538f2f" xlink:to="loc_mtb_ScheduleOfBorrowingsTable_019c76d5-3cfa-759a-9887-82da0c30320d" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LegalEntityAxis_019c76d5-3cfa-7c90-a8d2-2f3aa483397d" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_LegalEntityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_mtb_ScheduleOfBorrowingsTable_019c76d5-3cfa-759a-9887-82da0c30320d" xlink:to="loc_dei_LegalEntityAxis_019c76d5-3cfa-7c90-a8d2-2f3aa483397d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019c76d5-3cfa-7c90-a8d2-2f3aa483397d_default" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_019c76d5-3cfa-7c90-a8d2-2f3aa483397d" xlink:to="loc_dei_EntityDomain_019c76d5-3cfa-7c90-a8d2-2f3aa483397d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019c76d5-3cfa-790f-b3e1-cf3d8005f64a" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_019c76d5-3cfa-7c90-a8d2-2f3aa483397d" xlink:to="loc_dei_EntityDomain_019c76d5-3cfa-790f-b3e1-cf3d8005f64a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_MAndTMember_019c76d5-3cfa-7f3e-897e-32417b2cbeac" xlink:href="mtb-20260331.xsd#mtb_MAndTMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_019c76d5-3cfa-790f-b3e1-cf3d8005f64a" xlink:to="loc_mtb_MAndTMember_019c76d5-3cfa-7f3e-897e-32417b2cbeac" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeAxis_019dc040-1ad1-7e4c-b8a2-78f2559fcd64" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SubsequentEventTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_mtb_ScheduleOfBorrowingsTable_019c76d5-3cfa-759a-9887-82da0c30320d" xlink:to="loc_us-gaap_SubsequentEventTypeAxis_019dc040-1ad1-7e4c-b8a2-78f2559fcd64" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_019dc040-1ad1-7e4c-b8a2-78f2559fcd64_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_019dc040-1ad1-7e4c-b8a2-78f2559fcd64" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_019dc040-1ad1-7e4c-b8a2-78f2559fcd64_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_019dc040-1ad1-7c35-8d67-3eb4a0102d35" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_019dc040-1ad1-7e4c-b8a2-78f2559fcd64" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_019dc040-1ad1-7c35-8d67-3eb4a0102d35" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventMember_019dc040-417a-76c3-8989-e4147c213c5b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SubsequentEventMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventTypeDomain_019dc040-1ad1-7c35-8d67-3eb4a0102d35" xlink:to="loc_us-gaap_SubsequentEventMember_019dc040-417a-76c3-8989-e4147c213c5b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtCurrentAbstract_019c76d5-3cfa-7c88-8209-42929d26ce83" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtCurrentAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_mtb_ScheduleOfBorrowingsLineItems_019c76d5-3cfa-73b6-8369-f6c568538f2f" xlink:to="loc_us-gaap_DebtCurrentAbstract_019c76d5-3cfa-7c88-8209-42929d26ce83" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FederalFundsPurchasedAndSecuritiesSoldUnderAgreementsToRepurchase_019c76d5-3cfa-7255-a850-4b9df1aaa3d7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FederalFundsPurchasedAndSecuritiesSoldUnderAgreementsToRepurchase"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtCurrentAbstract_019c76d5-3cfa-7c88-8209-42929d26ce83" xlink:to="loc_us-gaap_FederalFundsPurchasedAndSecuritiesSoldUnderAgreementsToRepurchase_019c76d5-3cfa-7255-a850-4b9df1aaa3d7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FederalHomeLoanBankAdvancesMaturitiesSummaryDueWithinOneYearOfBalanceSheetDate_019c76d5-3cfa-7964-8506-d8d2f17ccbc5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FederalHomeLoanBankAdvancesMaturitiesSummaryDueWithinOneYearOfBalanceSheetDate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtCurrentAbstract_019c76d5-3cfa-7c88-8209-42929d26ce83" xlink:to="loc_us-gaap_FederalHomeLoanBankAdvancesMaturitiesSummaryDueWithinOneYearOfBalanceSheetDate_019c76d5-3cfa-7964-8506-d8d2f17ccbc5" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShortTermBorrowings_019c76d5-3cfa-73a9-9bba-c84382775cbc" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShortTermBorrowings"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtCurrentAbstract_019c76d5-3cfa-7c88-8209-42929d26ce83" xlink:to="loc_us-gaap_ShortTermBorrowings_019c76d5-3cfa-73a9-9bba-c84382775cbc" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtNoncurrentAbstract_019c76d5-3cfa-71c0-a565-757c7eb06fe7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongTermDebtNoncurrentAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_mtb_ScheduleOfBorrowingsLineItems_019c76d5-3cfa-73b6-8369-f6c568538f2f" xlink:to="loc_us-gaap_LongTermDebtNoncurrentAbstract_019c76d5-3cfa-71c0-a565-757c7eb06fe7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SeniorNotes_019c76d5-3cfa-7dfb-8acb-0418ab4777ae" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SeniorNotes"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongTermDebtNoncurrentAbstract_019c76d5-3cfa-71c0-a565-757c7eb06fe7" xlink:to="loc_us-gaap_SeniorNotes_019c76d5-3cfa-7dfb-8acb-0418ab4777ae" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FederalHomeLoanBankAdvancesLongTerm_019c76d5-3cfa-79d6-ac72-b2095746af2c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FederalHomeLoanBankAdvancesLongTerm"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongTermDebtNoncurrentAbstract_019c76d5-3cfa-71c0-a565-757c7eb06fe7" xlink:to="loc_us-gaap_FederalHomeLoanBankAdvancesLongTerm_019c76d5-3cfa-79d6-ac72-b2095746af2c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubordinatedDebt_019c76d5-3cfa-7b1a-875c-c62816e84b3f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SubordinatedDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongTermDebtNoncurrentAbstract_019c76d5-3cfa-71c0-a565-757c7eb06fe7" xlink:to="loc_us-gaap_SubordinatedDebt_019c76d5-3cfa-7b1a-875c-c62816e84b3f" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_JuniorSubordinatedNotes_019c76d5-3cfa-70fe-beb5-25ce3a89eeba" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_JuniorSubordinatedNotes"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongTermDebtNoncurrentAbstract_019c76d5-3cfa-71c0-a565-757c7eb06fe7" xlink:to="loc_us-gaap_JuniorSubordinatedNotes_019c76d5-3cfa-70fe-beb5-25ce3a89eeba" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SecuredLongTermDebt_019c76d5-3cfa-794d-b187-98df32451762" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SecuredLongTermDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongTermDebtNoncurrentAbstract_019c76d5-3cfa-71c0-a565-757c7eb06fe7" xlink:to="loc_us-gaap_SecuredLongTermDebt_019c76d5-3cfa-794d-b187-98df32451762" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherLongTermDebt_019c76d5-3cfa-72d9-8e12-a74bf540dc77" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherLongTermDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongTermDebtNoncurrentAbstract_019c76d5-3cfa-71c0-a565-757c7eb06fe7" xlink:to="loc_us-gaap_OtherLongTermDebt_019c76d5-3cfa-72d9-8e12-a74bf540dc77" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebt_019c76d5-3cfa-7d66-afb5-4c2d2fc66541" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongTermDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongTermDebtNoncurrentAbstract_019c76d5-3cfa-71c0-a565-757c7eb06fe7" xlink:to="loc_us-gaap_LongTermDebt_019c76d5-3cfa-7d66-afb5-4c2d2fc66541" xlink:type="arc" order="7"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.mtb.com/role/BorrowingsAdditionalInformationDetail" xlink:type="simple" xlink:href="mtb-20260331.xsd#BorrowingsAdditionalInformationDetail"/>
  <link:definitionLink xlink:role="http://www.mtb.com/role/BorrowingsAdditionalInformationDetail" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_019c76d5-3cfa-76ba-a10a-7020e4bd608f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_019c76d5-3cfa-7e03-9009-23dc50e39fb0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019c76d5-3cfa-76ba-a10a-7020e4bd608f" xlink:to="loc_us-gaap_DebtInstrumentTable_019c76d5-3cfa-7e03-9009-23dc50e39fb0" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityAxis_019c76d5-3cfa-7bd6-b2e0-cf8b46b091ff" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LineOfCreditFacilityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_019c76d5-3cfa-7e03-9009-23dc50e39fb0" xlink:to="loc_us-gaap_LineOfCreditFacilityAxis_019c76d5-3cfa-7bd6-b2e0-cf8b46b091ff" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityLenderDomain_019c76d5-3cfa-7bd6-b2e0-cf8b46b091ff_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LineOfCreditFacilityLenderDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LineOfCreditFacilityAxis_019c76d5-3cfa-7bd6-b2e0-cf8b46b091ff" xlink:to="loc_us-gaap_LineOfCreditFacilityLenderDomain_019c76d5-3cfa-7bd6-b2e0-cf8b46b091ff_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityLenderDomain_019c76d5-3cfa-79f2-bcd2-044e6b936c54" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LineOfCreditFacilityLenderDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LineOfCreditFacilityAxis_019c76d5-3cfa-7bd6-b2e0-cf8b46b091ff" xlink:to="loc_us-gaap_LineOfCreditFacilityLenderDomain_019c76d5-3cfa-79f2-bcd2-044e6b936c54" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_FrbOfNewYorkMember_019c76d5-3cfa-7f10-96ba-b2f73ca0b130" xlink:href="mtb-20260331.xsd#mtb_FrbOfNewYorkMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLenderDomain_019c76d5-3cfa-79f2-bcd2-044e6b936c54" xlink:to="loc_mtb_FrbOfNewYorkMember_019c76d5-3cfa-7f10-96ba-b2f73ca0b130" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_019db073-5da7-789e-a8fb-4c35668d0d4a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_019c76d5-3cfa-7e03-9009-23dc50e39fb0" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_019db073-5da7-789e-a8fb-4c35668d0d4a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_019db073-5da7-789e-a8fb-4c35668d0d4a_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_019db073-5da7-789e-a8fb-4c35668d0d4a" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_019db073-5da7-789e-a8fb-4c35668d0d4a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_019db073-5da7-7dc1-90ca-ff8860c6fd3f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_019db073-5da7-789e-a8fb-4c35668d0d4a" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_019db073-5da7-7dc1-90ca-ff8860c6fd3f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FederalHomeLoanBankAdvancesMember_019db073-5da7-7bb2-bf4f-95572fd255a3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FederalHomeLoanBankAdvancesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_019db073-5da7-7dc1-90ca-ff8860c6fd3f" xlink:to="loc_us-gaap_FederalHomeLoanBankAdvancesMember_019db073-5da7-7bb2-bf4f-95572fd255a3" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubordinatedDebtMember_019de4ab-4d61-79c2-b4c8-ad30a76cb92e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SubordinatedDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_019db073-5da7-7dc1-90ca-ff8860c6fd3f" xlink:to="loc_us-gaap_SubordinatedDebtMember_019de4ab-4d61-79c2-b4c8-ad30a76cb92e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeAxis_019dc040-6d55-7861-aa97-f51a7fa119d7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SubsequentEventTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_019c76d5-3cfa-7e03-9009-23dc50e39fb0" xlink:to="loc_us-gaap_SubsequentEventTypeAxis_019dc040-6d55-7861-aa97-f51a7fa119d7" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_019dc040-6d55-7861-aa97-f51a7fa119d7_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_019dc040-6d55-7861-aa97-f51a7fa119d7" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_019dc040-6d55-7861-aa97-f51a7fa119d7_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_019dc040-6d55-7591-a0c0-3d992ba75240" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_019dc040-6d55-7861-aa97-f51a7fa119d7" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_019dc040-6d55-7591-a0c0-3d992ba75240" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventMember_019dc040-6d55-7ca5-bb89-e7494ba3e76a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SubsequentEventMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventTypeDomain_019dc040-6d55-7591-a0c0-3d992ba75240" xlink:to="loc_us-gaap_SubsequentEventMember_019dc040-6d55-7ca5-bb89-e7494ba3e76a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LegalEntityAxis_019dc040-6d55-70eb-8101-97b227a4bbce" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_LegalEntityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_019c76d5-3cfa-7e03-9009-23dc50e39fb0" xlink:to="loc_dei_LegalEntityAxis_019dc040-6d55-70eb-8101-97b227a4bbce" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019dc040-6d55-70eb-8101-97b227a4bbce_default" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_019dc040-6d55-70eb-8101-97b227a4bbce" xlink:to="loc_dei_EntityDomain_019dc040-6d55-70eb-8101-97b227a4bbce_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019dc040-6d55-71bf-a841-7c9752bb3e9f" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_019dc040-6d55-70eb-8101-97b227a4bbce" xlink:to="loc_dei_EntityDomain_019dc040-6d55-71bf-a841-7c9752bb3e9f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_MAndTMember_019dc040-6d55-775d-92ff-fecc1bbceb93" xlink:href="mtb-20260331.xsd#mtb_MAndTMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_019dc040-6d55-71bf-a841-7c9752bb3e9f" xlink:to="loc_mtb_MAndTMember_019dc040-6d55-775d-92ff-fecc1bbceb93" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_019db073-5da7-7ac6-b3a3-c95fc1b6a52f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019c76d5-3cfa-76ba-a10a-7020e4bd608f" xlink:to="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_019db073-5da7-7ac6-b3a3-c95fc1b6a52f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCredit_019d4e63-68ca-74cd-984c-be064fc3d3bb" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LineOfCredit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019c76d5-3cfa-76ba-a10a-7020e4bd608f" xlink:to="loc_us-gaap_LineOfCredit_019d4e63-68ca-74cd-984c-be064fc3d3bb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityCurrentBorrowingCapacity_019c76d5-3cfa-744a-9532-1f0fdc8808e4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LineOfCreditFacilityCurrentBorrowingCapacity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019c76d5-3cfa-76ba-a10a-7020e4bd608f" xlink:to="loc_us-gaap_LineOfCreditFacilityCurrentBorrowingCapacity_019c76d5-3cfa-744a-9532-1f0fdc8808e4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentFaceAmount_019de4ac-41eb-7747-99e7-31c6c7659531" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentFaceAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019c76d5-3cfa-76ba-a10a-7020e4bd608f" xlink:to="loc_us-gaap_DebtInstrumentFaceAmount_019de4ac-41eb-7747-99e7-31c6c7659531" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_019dc040-6d55-7d30-999b-8eb0b22bc970" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentInterestRateStatedPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019c76d5-3cfa-76ba-a10a-7020e4bd608f" xlink:to="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_019dc040-6d55-7d30-999b-8eb0b22bc970" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTerm_019df356-6ade-72c7-bd5e-287ea22528b2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentTerm"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019c76d5-3cfa-76ba-a10a-7020e4bd608f" xlink:to="loc_us-gaap_DebtInstrumentTerm_019df356-6ade-72c7-bd5e-287ea22528b2" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_019dc040-6d55-7a01-ad7a-743c8404a9f7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentBasisSpreadOnVariableRate1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019c76d5-3cfa-76ba-a10a-7020e4bd608f" xlink:to="loc_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_019dc040-6d55-7a01-ad7a-743c8404a9f7" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SeniorNotes_019dc040-6d55-706f-880e-30c8517799a0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SeniorNotes"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019c76d5-3cfa-76ba-a10a-7020e4bd608f" xlink:to="loc_us-gaap_SeniorNotes_019dc040-6d55-706f-880e-30c8517799a0" xlink:type="arc" order="7"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.mtb.com/role/ShareholdersequityIssuedandOutstandingPreferredStockDetail" xlink:type="simple" xlink:href="mtb-20260331.xsd#ShareholdersequityIssuedandOutstandingPreferredStockDetail"/>
  <link:definitionLink xlink:role="http://www.mtb.com/role/ShareholdersequityIssuedandOutstandingPreferredStockDetail" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockLineItems_019c76d5-3cfa-7085-89b4-ab82c7bb4d0b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ClassOfStockLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfStockByClassTable_019c76d5-3cfa-75ff-b344-eacdd2494051" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfStockByClassTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ClassOfStockLineItems_019c76d5-3cfa-7085-89b4-ab82c7bb4d0b" xlink:to="loc_us-gaap_ScheduleOfStockByClassTable_019c76d5-3cfa-75ff-b344-eacdd2494051" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_019c76d5-3cfa-79c1-8db7-773f13733413" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfStockByClassTable_019c76d5-3cfa-75ff-b344-eacdd2494051" xlink:to="loc_us-gaap_StatementClassOfStockAxis_019c76d5-3cfa-79c1-8db7-773f13733413" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_019c76d5-3cfa-79c1-8db7-773f13733413_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_019c76d5-3cfa-79c1-8db7-773f13733413" xlink:to="loc_us-gaap_ClassOfStockDomain_019c76d5-3cfa-79c1-8db7-773f13733413_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_019c76d5-3cfa-77d1-a8bc-25547ae123e1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_019c76d5-3cfa-79c1-8db7-773f13733413" xlink:to="loc_us-gaap_ClassOfStockDomain_019c76d5-3cfa-77d1-a8bc-25547ae123e1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SeriesEPreferredStockMember_019c76d5-3cfa-7f78-b492-27c4c61d2790" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SeriesEPreferredStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_019c76d5-3cfa-77d1-a8bc-25547ae123e1" xlink:to="loc_us-gaap_SeriesEPreferredStockMember_019c76d5-3cfa-7f78-b492-27c4c61d2790" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SeriesFPreferredStockMember_019c76d5-3cfa-75b9-98c9-20f2e18c6b58" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SeriesFPreferredStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_019c76d5-3cfa-77d1-a8bc-25547ae123e1" xlink:to="loc_us-gaap_SeriesFPreferredStockMember_019c76d5-3cfa-75b9-98c9-20f2e18c6b58" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SeriesGPreferredStockMember_019c76d5-3cfa-7621-b83f-0f86e78574da" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SeriesGPreferredStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_019c76d5-3cfa-77d1-a8bc-25547ae123e1" xlink:to="loc_us-gaap_SeriesGPreferredStockMember_019c76d5-3cfa-7621-b83f-0f86e78574da" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SeriesHPreferredStockMember_019c76d5-3cfa-75e7-b61f-e0b87fdedc08" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SeriesHPreferredStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_019c76d5-3cfa-77d1-a8bc-25547ae123e1" xlink:to="loc_us-gaap_SeriesHPreferredStockMember_019c76d5-3cfa-75e7-b61f-e0b87fdedc08" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_SeriesIPreferredStocksMember_019c76d5-3cfa-7375-a51c-ad6f6dbf7566" xlink:href="mtb-20260331.xsd#mtb_SeriesIPreferredStocksMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_019c76d5-3cfa-77d1-a8bc-25547ae123e1" xlink:to="loc_mtb_SeriesIPreferredStocksMember_019c76d5-3cfa-7375-a51c-ad6f6dbf7566" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_SeriesJPreferredStockMember_019c76d5-3cfa-7399-83fa-b7d7b2d1af90" xlink:href="mtb-20260331.xsd#mtb_SeriesJPreferredStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_019c76d5-3cfa-77d1-a8bc-25547ae123e1" xlink:to="loc_mtb_SeriesJPreferredStockMember_019c76d5-3cfa-7399-83fa-b7d7b2d1af90" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_SeriesKPreferredStockMember_019d4e65-249b-7a2d-bab2-e6abd2a2d8fc" xlink:href="mtb-20260331.xsd#mtb_SeriesKPreferredStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_019c76d5-3cfa-77d1-a8bc-25547ae123e1" xlink:to="loc_mtb_SeriesKPreferredStockMember_019d4e65-249b-7a2d-bab2-e6abd2a2d8fc" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PreferredStockSharesIssued_019c76d5-3cfa-766a-9493-3f2c2a1a2097" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PreferredStockSharesIssued"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_019c76d5-3cfa-7085-89b4-ab82c7bb4d0b" xlink:to="loc_us-gaap_PreferredStockSharesIssued_019c76d5-3cfa-766a-9493-3f2c2a1a2097" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PreferredStockSharesOutstanding_019c76d5-3cfa-7aca-9575-0d3d284858cb" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PreferredStockSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_019c76d5-3cfa-7085-89b4-ab82c7bb4d0b" xlink:to="loc_us-gaap_PreferredStockSharesOutstanding_019c76d5-3cfa-7aca-9575-0d3d284858cb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PreferredStockLiquidationPreference_019c76d5-3cfa-7311-b401-8578dd77c3d9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PreferredStockLiquidationPreference"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_019c76d5-3cfa-7085-89b4-ab82c7bb4d0b" xlink:to="loc_us-gaap_PreferredStockLiquidationPreference_019c76d5-3cfa-7311-b401-8578dd77c3d9" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PreferredStockDividendRatePercentage_019c76d5-3cfa-7898-a76e-772842c9135e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PreferredStockDividendRatePercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_019c76d5-3cfa-7085-89b4-ab82c7bb4d0b" xlink:to="loc_us-gaap_PreferredStockDividendRatePercentage_019c76d5-3cfa-7898-a76e-772842c9135e" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PreferredStockValue_019c76d5-3cfa-71dc-8914-d0774f7bc1c4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PreferredStockValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_019c76d5-3cfa-7085-89b4-ab82c7bb4d0b" xlink:to="loc_us-gaap_PreferredStockValue_019c76d5-3cfa-71dc-8914-d0774f7bc1c4" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PreferredStockDividendsPerShareDeclared_019c76d5-3cfa-7c98-bc2a-b57415f62848" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PreferredStockDividendsPerShareDeclared"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_019c76d5-3cfa-7085-89b4-ab82c7bb4d0b" xlink:to="loc_us-gaap_PreferredStockDividendsPerShareDeclared_019c76d5-3cfa-7c98-bc2a-b57415f62848" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_PreferredStockDividendRateSpreadPercent_019c76d5-3cfa-7984-91a1-d5077a56412d" xlink:href="mtb-20260331.xsd#mtb_PreferredStockDividendRateSpreadPercent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_019c76d5-3cfa-7085-89b4-ab82c7bb4d0b" xlink:to="loc_mtb_PreferredStockDividendRateSpreadPercent_019c76d5-3cfa-7984-91a1-d5077a56412d" xlink:type="arc" order="6"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.mtb.com/role/RevenuefromcontractswithcustomersAdditionalInformationDetails" xlink:type="simple" xlink:href="mtb-20260331.xsd#RevenuefromcontractswithcustomersAdditionalInformationDetails"/>
  <link:definitionLink xlink:role="http://www.mtb.com/role/RevenuefromcontractswithcustomersAdditionalInformationDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueLineItems_019c76d5-3cfa-74b9-9967-59d69288864d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DisaggregationOfRevenueLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueTable_019c76d5-3cfa-7329-975e-e74f86e3436e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DisaggregationOfRevenueTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_019c76d5-3cfa-74b9-9967-59d69288864d" xlink:to="loc_us-gaap_DisaggregationOfRevenueTable_019c76d5-3cfa-7329-975e-e74f86e3436e" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionStartDateAxis_019c76d5-3cfa-725a-b717-446f90c0b96a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionStartDateAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_019c76d5-3cfa-7329-975e-e74f86e3436e" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionStartDateAxis_019c76d5-3cfa-725a-b717-446f90c0b96a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_019c76d5-3cfa-7c46-99be-6475f861e4d1" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_019c76d5-3cfa-7329-975e-e74f86e3436e" xlink:to="loc_srt_RangeAxis_019c76d5-3cfa-7c46-99be-6475f861e4d1" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_019c76d5-3cfa-7c46-99be-6475f861e4d1_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_019c76d5-3cfa-7c46-99be-6475f861e4d1" xlink:to="loc_srt_RangeMember_019c76d5-3cfa-7c46-99be-6475f861e4d1_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_019c76d5-3cfa-7149-ab34-5c9e0520ed48" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_019c76d5-3cfa-7c46-99be-6475f861e4d1" xlink:to="loc_srt_RangeMember_019c76d5-3cfa-7149-ab34-5c9e0520ed48" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_019c76d5-3cfa-7f75-a1d2-b25b0e8c6b85" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_019c76d5-3cfa-7149-ab34-5c9e0520ed48" xlink:to="loc_srt_MaximumMember_019c76d5-3cfa-7f75-a1d2-b25b0e8c6b85" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1_019c76d5-3cfa-747d-b778-2ae13f6f96ee" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_019c76d5-3cfa-74b9-9967-59d69288864d" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1_019c76d5-3cfa-747d-b778-2ae13f6f96ee" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligation_019c76d5-3cfa-79eb-a8cf-cc8337595b6c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RevenueRemainingPerformanceObligation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_019c76d5-3cfa-74b9-9967-59d69288864d" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligation_019c76d5-3cfa-79eb-a8cf-cc8337595b6c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerLiability_019c76d5-3cfa-7702-9cd6-e48be8162922" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ContractWithCustomerLiability"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_019c76d5-3cfa-74b9-9967-59d69288864d" xlink:to="loc_us-gaap_ContractWithCustomerLiability_019c76d5-3cfa-7702-9cd6-e48be8162922" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.mtb.com/role/RevenuefromcontractswithcustomersAdditionalInformationDetails_1" xlink:type="simple" xlink:href="mtb-20260331.xsd#RevenuefromcontractswithcustomersAdditionalInformationDetails_1"/>
  <link:definitionLink xlink:role="http://www.mtb.com/role/RevenuefromcontractswithcustomersAdditionalInformationDetails_1" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueLineItems_019c76d5-3cfa-74b9-9967-59d69288864d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DisaggregationOfRevenueLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueTable_019c76d5-3cfa-7329-975e-e74f86e3436e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DisaggregationOfRevenueTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_019c76d5-3cfa-74b9-9967-59d69288864d" xlink:to="loc_us-gaap_DisaggregationOfRevenueTable_019c76d5-3cfa-7329-975e-e74f86e3436e" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_019c76d5-3cfa-7c46-99be-6475f861e4d1" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_019c76d5-3cfa-7329-975e-e74f86e3436e" xlink:to="loc_srt_RangeAxis_019c76d5-3cfa-7c46-99be-6475f861e4d1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_019c76d5-3cfa-7c46-99be-6475f861e4d1_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_019c76d5-3cfa-7c46-99be-6475f861e4d1" xlink:to="loc_srt_RangeMember_019c76d5-3cfa-7c46-99be-6475f861e4d1_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_019c76d5-3cfa-7149-ab34-5c9e0520ed48" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_019c76d5-3cfa-7c46-99be-6475f861e4d1" xlink:to="loc_srt_RangeMember_019c76d5-3cfa-7149-ab34-5c9e0520ed48" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_019c76d5-3cfa-7f75-a1d2-b25b0e8c6b85" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_019c76d5-3cfa-7149-ab34-5c9e0520ed48" xlink:to="loc_srt_MaximumMember_019c76d5-3cfa-7f75-a1d2-b25b0e8c6b85" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1_019c76d5-3cfa-747d-b778-2ae13f6f96ee" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_019c76d5-3cfa-74b9-9967-59d69288864d" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1_019c76d5-3cfa-747d-b778-2ae13f6f96ee" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligation_019c76d5-3cfa-79eb-a8cf-cc8337595b6c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RevenueRemainingPerformanceObligation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_019c76d5-3cfa-74b9-9967-59d69288864d" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligation_019c76d5-3cfa-79eb-a8cf-cc8337595b6c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerLiability_019c76d5-3cfa-7702-9cd6-e48be8162922" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ContractWithCustomerLiability"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_019c76d5-3cfa-74b9-9967-59d69288864d" xlink:to="loc_us-gaap_ContractWithCustomerLiability_019c76d5-3cfa-7702-9cd6-e48be8162922" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.mtb.com/role/RevenuefromcontractswithcustomersSummaryofSourcesofNoninterestIncomethatareSubjecttoRevenueRecognitionAccountingGuidanceDetails" xlink:type="simple" xlink:href="mtb-20260331.xsd#RevenuefromcontractswithcustomersSummaryofSourcesofNoninterestIncomethatareSubjecttoRevenueRecognitionAccountingGuidanceDetails"/>
  <link:definitionLink xlink:role="http://www.mtb.com/role/RevenuefromcontractswithcustomersSummaryofSourcesofNoninterestIncomethatareSubjecttoRevenueRecognitionAccountingGuidanceDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueLineItems_019c76d5-3cfa-7ff7-b5ef-a18694586b4d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DisaggregationOfRevenueLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueTable_019c76d5-3cfa-7f43-9661-2cff1f8ab985" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DisaggregationOfRevenueTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_019c76d5-3cfa-7ff7-b5ef-a18694586b4d" xlink:to="loc_us-gaap_DisaggregationOfRevenueTable_019c76d5-3cfa-7f43-9661-2cff1f8ab985" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_019c76d5-3cfa-7924-a1d9-08c7abe95e63" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_019c76d5-3cfa-7f43-9661-2cff1f8ab985" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_019c76d5-3cfa-7924-a1d9-08c7abe95e63" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_019c76d5-3cfa-7924-a1d9-08c7abe95e63_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_019c76d5-3cfa-7924-a1d9-08c7abe95e63" xlink:to="loc_us-gaap_SegmentDomain_019c76d5-3cfa-7924-a1d9-08c7abe95e63_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_019c76d5-3cfa-7f1d-b8d4-525dbf9d3a53" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_019c76d5-3cfa-7924-a1d9-08c7abe95e63" xlink:to="loc_us-gaap_SegmentDomain_019c76d5-3cfa-7f1d-b8d4-525dbf9d3a53" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_CommercialBankingMember_019c76d5-3cfa-7693-88b5-f5b543f32f9b" xlink:href="mtb-20260331.xsd#mtb_CommercialBankingMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_019c76d5-3cfa-7f1d-b8d4-525dbf9d3a53" xlink:to="loc_mtb_CommercialBankingMember_019c76d5-3cfa-7693-88b5-f5b543f32f9b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_RetailBankingMember_019c76d5-3cfa-7f7a-b180-1ab802aefdb4" xlink:href="mtb-20260331.xsd#mtb_RetailBankingMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_019c76d5-3cfa-7f1d-b8d4-525dbf9d3a53" xlink:to="loc_mtb_RetailBankingMember_019c76d5-3cfa-7f7a-b180-1ab802aefdb4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_InstitutionalServicesAndWealthManagementMember_019c76d5-3cfa-7eb7-ae7c-f8907db7aaa2" xlink:href="mtb-20260331.xsd#mtb_InstitutionalServicesAndWealthManagementMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_019c76d5-3cfa-7f1d-b8d4-525dbf9d3a53" xlink:to="loc_mtb_InstitutionalServicesAndWealthManagementMember_019c76d5-3cfa-7eb7-ae7c-f8907db7aaa2" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_019c76d5-3cfa-77ad-97cd-afce8159bc97" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ProductOrServiceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_019c76d5-3cfa-7f43-9661-2cff1f8ab985" xlink:to="loc_srt_ProductOrServiceAxis_019c76d5-3cfa-77ad-97cd-afce8159bc97" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_019c76d5-3cfa-77ad-97cd-afce8159bc97_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_019c76d5-3cfa-77ad-97cd-afce8159bc97" xlink:to="loc_srt_ProductsAndServicesDomain_019c76d5-3cfa-77ad-97cd-afce8159bc97_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_019c76d5-3cfa-7569-84ce-2c2498bf9622" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_019c76d5-3cfa-77ad-97cd-afce8159bc97" xlink:to="loc_srt_ProductsAndServicesDomain_019c76d5-3cfa-7569-84ce-2c2498bf9622" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DepositAccountMember_019c76d5-3cfa-7a06-8eec-c475c5f16c8a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DepositAccountMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_019c76d5-3cfa-7569-84ce-2c2498bf9622" xlink:to="loc_us-gaap_DepositAccountMember_019c76d5-3cfa-7a06-8eec-c475c5f16c8a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiduciaryAndTrustMember_019c76d5-3cfa-7fce-8700-2cf7b6fcd78c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FiduciaryAndTrustMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_019c76d5-3cfa-7569-84ce-2c2498bf9622" xlink:to="loc_us-gaap_FiduciaryAndTrustMember_019c76d5-3cfa-7fce-8700-2cf7b6fcd78c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_BrokerageServicesIncomeMember_019c76d5-3cfa-765c-882e-99ee29e4a74f" xlink:href="mtb-20260331.xsd#mtb_BrokerageServicesIncomeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_019c76d5-3cfa-7569-84ce-2c2498bf9622" xlink:to="loc_mtb_BrokerageServicesIncomeMember_019c76d5-3cfa-765c-882e-99ee29e4a74f" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditCardMerchantDiscountMember_019c76d5-3cfa-7156-8382-2830fdaac34d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CreditCardMerchantDiscountMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_019c76d5-3cfa-7569-84ce-2c2498bf9622" xlink:to="loc_us-gaap_CreditCardMerchantDiscountMember_019c76d5-3cfa-7156-8382-2830fdaac34d" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProductAndServiceOtherMember_019c76d5-3cfa-738f-afd7-9fe9752bf828" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ProductAndServiceOtherMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_019c76d5-3cfa-7569-84ce-2c2498bf9622" xlink:to="loc_us-gaap_ProductAndServiceOtherMember_019c76d5-3cfa-738f-afd7-9fe9752bf828" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_019c76d5-3cfa-78dd-bb52-4495a54e026e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_019c76d5-3cfa-7ff7-b5ef-a18694586b4d" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_019c76d5-3cfa-78dd-bb52-4495a54e026e" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.mtb.com/role/PensionplansandotherpostretirementbenefitsNetPeriodicDefinedBenefitCostforDefinedBenefitPlansDetail" xlink:type="simple" xlink:href="mtb-20260331.xsd#PensionplansandotherpostretirementbenefitsNetPeriodicDefinedBenefitCostforDefinedBenefitPlansDetail"/>
  <link:definitionLink xlink:role="http://www.mtb.com/role/PensionplansandotherpostretirementbenefitsNetPeriodicDefinedBenefitCostforDefinedBenefitPlansDetail" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_019c76d5-3cfa-7583-b22f-0910234c9db3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DefinedBenefitPlanDisclosureLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_019c76d5-3cfa-7fec-8aba-0b41c2b15abc" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_019c76d5-3cfa-7583-b22f-0910234c9db3" xlink:to="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_019c76d5-3cfa-7fec-8aba-0b41c2b15abc" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetirementPlanTypeAxis_019c76d5-3cfa-767b-aea7-c0494428028e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RetirementPlanTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_019c76d5-3cfa-7fec-8aba-0b41c2b15abc" xlink:to="loc_us-gaap_RetirementPlanTypeAxis_019c76d5-3cfa-767b-aea7-c0494428028e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetirementPlanTypeDomain_019c76d5-3cfa-767b-aea7-c0494428028e_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RetirementPlanTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RetirementPlanTypeAxis_019c76d5-3cfa-767b-aea7-c0494428028e" xlink:to="loc_us-gaap_RetirementPlanTypeDomain_019c76d5-3cfa-767b-aea7-c0494428028e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetirementPlanTypeDomain_019c76d5-3cfa-71b3-a9eb-3f5b8d50c8fa" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RetirementPlanTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RetirementPlanTypeAxis_019c76d5-3cfa-767b-aea7-c0494428028e" xlink:to="loc_us-gaap_RetirementPlanTypeDomain_019c76d5-3cfa-71b3-a9eb-3f5b8d50c8fa" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PensionPlansDefinedBenefitMember_019c76d5-3cfa-70c1-88ac-4e0b3d62d940" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PensionPlansDefinedBenefitMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RetirementPlanTypeDomain_019c76d5-3cfa-71b3-a9eb-3f5b8d50c8fa" xlink:to="loc_us-gaap_PensionPlansDefinedBenefitMember_019c76d5-3cfa-70c1-88ac-4e0b3d62d940" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember_019c76d5-3cfa-7b42-8f0c-525e46a629f3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RetirementPlanTypeDomain_019c76d5-3cfa-71b3-a9eb-3f5b8d50c8fa" xlink:to="loc_us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember_019c76d5-3cfa-7b42-8f0c-525e46a629f3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanServiceCost_019c76d5-3cfa-7b2d-8ce7-47d2c49a1ae7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DefinedBenefitPlanServiceCost"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_019c76d5-3cfa-7583-b22f-0910234c9db3" xlink:to="loc_us-gaap_DefinedBenefitPlanServiceCost_019c76d5-3cfa-7b2d-8ce7-47d2c49a1ae7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanInterestCost_019c76d5-3cfa-73b0-b125-8e20d2548382" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DefinedBenefitPlanInterestCost"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_019c76d5-3cfa-7583-b22f-0910234c9db3" xlink:to="loc_us-gaap_DefinedBenefitPlanInterestCost_019c76d5-3cfa-73b0-b125-8e20d2548382" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanExpectedReturnOnPlanAssets_019c76d5-3cfa-734e-85a3-0fe97cbcce48" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DefinedBenefitPlanExpectedReturnOnPlanAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_019c76d5-3cfa-7583-b22f-0910234c9db3" xlink:to="loc_us-gaap_DefinedBenefitPlanExpectedReturnOnPlanAssets_019c76d5-3cfa-734e-85a3-0fe97cbcce48" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanAmortizationOfGainsLosses_019c76d5-3cfa-7161-975b-01670dbdbf3b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DefinedBenefitPlanAmortizationOfGainsLosses"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_019c76d5-3cfa-7583-b22f-0910234c9db3" xlink:to="loc_us-gaap_DefinedBenefitPlanAmortizationOfGainsLosses_019c76d5-3cfa-7161-975b-01670dbdbf3b" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanNetPeriodicBenefitCost_019c76d5-3cfa-7a9b-821f-653cfa8f64f8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DefinedBenefitPlanNetPeriodicBenefitCost"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_019c76d5-3cfa-7583-b22f-0910234c9db3" xlink:to="loc_us-gaap_DefinedBenefitPlanNetPeriodicBenefitCost_019c76d5-3cfa-7a9b-821f-653cfa8f64f8" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanNetPeriodicBenefitCostCreditExcludingServiceCostStatementOfIncomeOrComprehensiveIncomeExtensibleList_019c76d5-3cfa-7871-84ea-cf0ce38a7341" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DefinedBenefitPlanNetPeriodicBenefitCostCreditExcludingServiceCostStatementOfIncomeOrComprehensiveIncomeExtensibleList"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_019c76d5-3cfa-7583-b22f-0910234c9db3" xlink:to="loc_us-gaap_DefinedBenefitPlanNetPeriodicBenefitCostCreditExcludingServiceCostStatementOfIncomeOrComprehensiveIncomeExtensibleList_019c76d5-3cfa-7871-84ea-cf0ce38a7341" xlink:type="arc" order="5"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.mtb.com/role/ComprehensiveincomeComponentsofOtherComprehensiveIncomeLossandAmountsReclassifiedfromAccumulatedOtherComprehensiveIncomeLosstoNetIncomeDetail" xlink:type="simple" xlink:href="mtb-20260331.xsd#ComprehensiveincomeComponentsofOtherComprehensiveIncomeLossandAmountsReclassifiedfromAccumulatedOtherComprehensiveIncomeLosstoNetIncomeDetail"/>
  <link:definitionLink xlink:role="http://www.mtb.com/role/ComprehensiveincomeComponentsofOtherComprehensiveIncomeLossandAmountsReclassifiedfromAccumulatedOtherComprehensiveIncomeLosstoNetIncomeDetail" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_019c76d5-3dc0-7f56-a566-0cf2cd8969ee" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_019c76d5-3dc0-7693-bd02-095e091fea1c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_019c76d5-3dc0-7f56-a566-0cf2cd8969ee" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_019c76d5-3dc0-7693-bd02-095e091fea1c" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_019c76d5-3dc0-7c9a-8b92-7904356a4ef9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_019c76d5-3dc0-7693-bd02-095e091fea1c" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_019c76d5-3dc0-7c9a-8b92-7904356a4ef9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_019c76d5-3dc0-7c9a-8b92-7904356a4ef9_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_019c76d5-3dc0-7c9a-8b92-7904356a4ef9" xlink:to="loc_us-gaap_EquityComponentDomain_019c76d5-3dc0-7c9a-8b92-7904356a4ef9_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_019c76d5-3dc0-72e3-8898-392085d36d07" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_019c76d5-3dc0-7c9a-8b92-7904356a4ef9" xlink:to="loc_us-gaap_EquityComponentDomain_019c76d5-3dc0-72e3-8898-392085d36d07" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_019c76d5-3dc0-756b-bcf7-a5629b18e52a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019c76d5-3dc0-72e3-8898-392085d36d07" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_019c76d5-3dc0-756b-bcf7-a5629b18e52a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedNetUnrealizedInvestmentGainLossMember_019c76d5-3dc0-787d-ae77-a490d0580143" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccumulatedNetUnrealizedInvestmentGainLossMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_019c76d5-3dc0-756b-bcf7-a5629b18e52a" xlink:to="loc_us-gaap_AccumulatedNetUnrealizedInvestmentGainLossMember_019c76d5-3dc0-787d-ae77-a490d0580143" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedGainLossNetCashFlowHedgeParentMember_019c76d5-3dc0-7feb-852a-ad54a4dabb3b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccumulatedGainLossNetCashFlowHedgeParentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_019c76d5-3dc0-756b-bcf7-a5629b18e52a" xlink:to="loc_us-gaap_AccumulatedGainLossNetCashFlowHedgeParentMember_019c76d5-3dc0-7feb-852a-ad54a4dabb3b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember_019c76d5-3dc0-7128-a424-ff76626354d7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_019c76d5-3dc0-756b-bcf7-a5629b18e52a" xlink:to="loc_us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember_019c76d5-3dc0-7128-a424-ff76626354d7" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedDefinedBenefitPlansAdjustmentNetPriorServiceCostCreditMember_019c76d5-3dc0-75a4-8e9e-d1602072e1a7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccumulatedDefinedBenefitPlansAdjustmentNetPriorServiceCostCreditMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember_019c76d5-3dc0-7128-a424-ff76626354d7" xlink:to="loc_us-gaap_AccumulatedDefinedBenefitPlansAdjustmentNetPriorServiceCostCreditMember_019c76d5-3dc0-75a4-8e9e-d1602072e1a7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_AccumulatedOtherMember_019c76d5-3dc0-795b-9bc4-080a37fdb7e0" xlink:href="mtb-20260331.xsd#mtb_AccumulatedOtherMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_019c76d5-3dc0-756b-bcf7-a5629b18e52a" xlink:to="loc_mtb_AccumulatedOtherMember_019c76d5-3dc0-795b-9bc4-080a37fdb7e0" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_019c76d5-3dc0-7e07-9568-14a8fbb84582" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AOCIAttributableToParentNetOfTaxRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_019c76d5-3dc0-7f56-a566-0cf2cd8969ee" xlink:to="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_019c76d5-3dc0-7e07-9568-14a8fbb84582" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_EquityAttributableToParentBeforeTax_019c76d5-3dc0-7165-94ab-bc76c87532ba" xlink:href="mtb-20260331.xsd#mtb_EquityAttributableToParentBeforeTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_019c76d5-3dc0-7e07-9568-14a8fbb84582" xlink:to="loc_mtb_EquityAttributableToParentBeforeTax_019c76d5-3dc0-7165-94ab-bc76c87532ba" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_EquityAttributableToParentTax_019c76d5-3dc0-72f6-a9d0-80264e516171" xlink:href="mtb-20260331.xsd#mtb_EquityAttributableToParentTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_019c76d5-3dc0-7e07-9568-14a8fbb84582" xlink:to="loc_mtb_EquityAttributableToParentTax_019c76d5-3dc0-72f6-a9d0-80264e516171" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_019c76d5-3dc0-7d92-bddb-420409d1c1f6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockholdersEquity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_019c76d5-3dc0-7e07-9568-14a8fbb84582" xlink:to="loc_us-gaap_StockholdersEquity_019c76d5-3dc0-7d92-bddb-420409d1c1f6" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OciBeforeReclassificationsBeforeTaxAttributableToParent_019c76d5-3dc0-7d98-9abf-cd76a8130e6c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OciBeforeReclassificationsBeforeTaxAttributableToParent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_019c76d5-3dc0-7e07-9568-14a8fbb84582" xlink:to="loc_us-gaap_OciBeforeReclassificationsBeforeTaxAttributableToParent_019c76d5-3dc0-7d98-9abf-cd76a8130e6c" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsTax_019c76d5-3dc0-7bf6-92a5-2a0b0f754492" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_019c76d5-3dc0-7e07-9568-14a8fbb84582" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsTax_019c76d5-3dc0-7bf6-92a5-2a0b0f754492" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OciBeforeReclassificationsNetOfTaxAttributableToParent_019c76d5-3dc0-798e-9b9c-28ac0f38c3ef" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OciBeforeReclassificationsNetOfTaxAttributableToParent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_019c76d5-3dc0-7e07-9568-14a8fbb84582" xlink:to="loc_us-gaap_OciBeforeReclassificationsNetOfTaxAttributableToParent_019c76d5-3dc0-798e-9b9c-28ac0f38c3ef" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReclassificationFromAociCurrentPeriodBeforeTaxAttributableToParent_019c76d5-3dc0-7e8c-927c-89ddaaa6c29b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ReclassificationFromAociCurrentPeriodBeforeTaxAttributableToParent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_019c76d5-3dc0-7e07-9568-14a8fbb84582" xlink:to="loc_us-gaap_ReclassificationFromAociCurrentPeriodBeforeTaxAttributableToParent_019c76d5-3dc0-7e8c-927c-89ddaaa6c29b" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReclassificationFromAociCurrentPeriodTax_019c76d5-3dc0-7f4b-bc60-033daa48dd03" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ReclassificationFromAociCurrentPeriodTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_019c76d5-3dc0-7e07-9568-14a8fbb84582" xlink:to="loc_us-gaap_ReclassificationFromAociCurrentPeriodTax_019c76d5-3dc0-7f4b-bc60-033daa48dd03" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReclassificationFromAociCurrentPeriodNetOfTaxAttributableToParent_019c76d5-3dc0-77c8-a07a-c0b725296487" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ReclassificationFromAociCurrentPeriodNetOfTaxAttributableToParent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_019c76d5-3dc0-7e07-9568-14a8fbb84582" xlink:to="loc_us-gaap_ReclassificationFromAociCurrentPeriodNetOfTaxAttributableToParent_019c76d5-3dc0-77c8-a07a-c0b725296487" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossBeforeTaxPortionAttributableToParent_019c76d5-3dc0-74a5-895d-4abcb24bd217" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherComprehensiveIncomeLossBeforeTaxPortionAttributableToParent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_019c76d5-3dc0-7e07-9568-14a8fbb84582" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossBeforeTaxPortionAttributableToParent_019c76d5-3dc0-74a5-895d-4abcb24bd217" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredIncomeTaxesAndTaxCredits_019c76d5-3dc0-714b-abee-64cbbea1734f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DeferredIncomeTaxesAndTaxCredits"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_019c76d5-3dc0-7e07-9568-14a8fbb84582" xlink:to="loc_us-gaap_DeferredIncomeTaxesAndTaxCredits_019c76d5-3dc0-714b-abee-64cbbea1734f" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent_019c76d5-3dc0-7787-8912-e92b84ac7894" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_019c76d5-3dc0-7e07-9568-14a8fbb84582" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent_019c76d5-3dc0-7787-8912-e92b84ac7894" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_EquityAttributableToParentBeforeTax_019c76d5-3dc0-7ba3-97b3-87067cd25da4" xlink:href="mtb-20260331.xsd#mtb_EquityAttributableToParentBeforeTax"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_EquityAttributableToParentTax_019c76d5-3dc0-7614-9892-956a7cde31ac" xlink:href="mtb-20260331.xsd#mtb_EquityAttributableToParentTax"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_019c76d5-3dc0-733a-bd8e-a846ceb10cdb" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockholdersEquity"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.mtb.com/role/ComprehensiveincomeAccumulatedOtherComprehensiveIncomeLossNetDetail" xlink:type="simple" xlink:href="mtb-20260331.xsd#ComprehensiveincomeAccumulatedOtherComprehensiveIncomeLossNetDetail"/>
  <link:definitionLink xlink:role="http://www.mtb.com/role/ComprehensiveincomeAccumulatedOtherComprehensiveIncomeLossNetDetail" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_019c76d5-3dc0-7604-80cf-055c48b29307" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_019c76d5-3dc0-7931-b6b5-1ee1f5a6327a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_019c76d5-3dc0-7604-80cf-055c48b29307" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_019c76d5-3dc0-7931-b6b5-1ee1f5a6327a" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_019c76d5-3dc0-72ea-aaf8-0c1c64896be2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_019c76d5-3dc0-7931-b6b5-1ee1f5a6327a" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_019c76d5-3dc0-72ea-aaf8-0c1c64896be2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_019c76d5-3dc0-72ea-aaf8-0c1c64896be2_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_019c76d5-3dc0-72ea-aaf8-0c1c64896be2" xlink:to="loc_us-gaap_EquityComponentDomain_019c76d5-3dc0-72ea-aaf8-0c1c64896be2_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_019c76d5-3dc0-767e-af78-272193456ead" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_019c76d5-3dc0-72ea-aaf8-0c1c64896be2" xlink:to="loc_us-gaap_EquityComponentDomain_019c76d5-3dc0-767e-af78-272193456ead" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedNetUnrealizedInvestmentGainLossMember_019c76d5-3dc0-7a43-a846-aac2b2a37f07" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccumulatedNetUnrealizedInvestmentGainLossMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019c76d5-3dc0-767e-af78-272193456ead" xlink:to="loc_us-gaap_AccumulatedNetUnrealizedInvestmentGainLossMember_019c76d5-3dc0-7a43-a846-aac2b2a37f07" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedGainLossNetCashFlowHedgeParentMember_019c76d5-3dc0-78ae-8a57-a493a5a83c53" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccumulatedGainLossNetCashFlowHedgeParentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019c76d5-3dc0-767e-af78-272193456ead" xlink:to="loc_us-gaap_AccumulatedGainLossNetCashFlowHedgeParentMember_019c76d5-3dc0-78ae-8a57-a493a5a83c53" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember_019c76d5-3dc0-7684-80e4-91d8490dfd9a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019c76d5-3dc0-767e-af78-272193456ead" xlink:to="loc_us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember_019c76d5-3dc0-7684-80e4-91d8490dfd9a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_AccumulatedOtherMember_019c76d5-3dc0-75a5-936f-2c71b168b54b" xlink:href="mtb-20260331.xsd#mtb_AccumulatedOtherMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019c76d5-3dc0-767e-af78-272193456ead" xlink:to="loc_mtb_AccumulatedOtherMember_019c76d5-3dc0-75a5-936f-2c71b168b54b" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_019c76d5-3dc0-7363-9889-73a611144813" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019c76d5-3dc0-767e-af78-272193456ead" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_019c76d5-3dc0-7363-9889-73a611144813" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_019c76d5-3dc0-7bed-a08d-f9c977bd7e53" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AOCIAttributableToParentNetOfTaxRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_019c76d5-3dc0-7604-80cf-055c48b29307" xlink:to="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_019c76d5-3dc0-7bed-a08d-f9c977bd7e53" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_019c76d5-3dc0-7013-a32f-0513e0727cbf" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockholdersEquity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_019c76d5-3dc0-7bed-a08d-f9c977bd7e53" xlink:to="loc_us-gaap_StockholdersEquity_019c76d5-3dc0-7013-a32f-0513e0727cbf" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent_019c76d5-3dc0-76a7-892d-c11cf3f57e46" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_019c76d5-3dc0-7bed-a08d-f9c977bd7e53" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent_019c76d5-3dc0-76a7-892d-c11cf3f57e46" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_019c76d5-3dc0-7bd7-a761-ce48c259ffc1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockholdersEquity"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.mtb.com/role/DerivativefinancialinstrumentsInformationaboutInterestRateSwapAgreementsDetail" xlink:type="simple" xlink:href="mtb-20260331.xsd#DerivativefinancialinstrumentsInformationaboutInterestRateSwapAgreementsDetail"/>
  <link:definitionLink xlink:role="http://www.mtb.com/role/DerivativefinancialinstrumentsInformationaboutInterestRateSwapAgreementsDetail" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeLineItems_019c76d5-3dc0-7967-9a73-b52024ad4ec9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeTable_019c76d5-3dc0-715d-a34a-ba70c4582c42" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DerivativeLineItems_019c76d5-3dc0-7967-9a73-b52024ad4ec9" xlink:to="loc_us-gaap_DerivativeTable_019c76d5-3dc0-715d-a34a-ba70c4582c42" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TradingActivityByTypeAxis_019c76d5-3dc0-70b0-97ab-57e66e1c9c3a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TradingActivityByTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeTable_019c76d5-3dc0-715d-a34a-ba70c4582c42" xlink:to="loc_us-gaap_TradingActivityByTypeAxis_019c76d5-3dc0-70b0-97ab-57e66e1c9c3a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TradingActivityByTypeDomain_019c76d5-3dc0-70b0-97ab-57e66e1c9c3a_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TradingActivityByTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_TradingActivityByTypeAxis_019c76d5-3dc0-70b0-97ab-57e66e1c9c3a" xlink:to="loc_us-gaap_TradingActivityByTypeDomain_019c76d5-3dc0-70b0-97ab-57e66e1c9c3a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TradingActivityByTypeDomain_019c76d5-3dc0-7125-a1c2-c4cc46cfd214" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TradingActivityByTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_TradingActivityByTypeAxis_019c76d5-3dc0-70b0-97ab-57e66e1c9c3a" xlink:to="loc_us-gaap_TradingActivityByTypeDomain_019c76d5-3dc0-7125-a1c2-c4cc46cfd214" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_FixedRateLongTermBorrowingsMember_019c76d5-3dc0-731e-b900-9d6e0cb037be" xlink:href="mtb-20260331.xsd#mtb_FixedRateLongTermBorrowingsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TradingActivityByTypeDomain_019c76d5-3dc0-7125-a1c2-c4cc46cfd214" xlink:to="loc_mtb_FixedRateLongTermBorrowingsMember_019c76d5-3dc0-731e-b900-9d6e0cb037be" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentAxis_019c76d5-3dc0-733b-bd5e-c81939d524ba" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancialInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeTable_019c76d5-3dc0-715d-a34a-ba70c4582c42" xlink:to="loc_us-gaap_FinancialInstrumentAxis_019c76d5-3dc0-733b-bd5e-c81939d524ba" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019c76d5-3dc0-733b-bd5e-c81939d524ba_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_019c76d5-3dc0-733b-bd5e-c81939d524ba" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019c76d5-3dc0-733b-bd5e-c81939d524ba_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019c76d5-3dc0-771d-9c98-f69a0099edff" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_019c76d5-3dc0-733b-bd5e-c81939d524ba" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019c76d5-3dc0-771d-9c98-f69a0099edff" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_InterestPaymentsOnVariableRateCommercialRealEstateLoansMember_019c76d5-3dc0-7a26-bf8a-2e54f5633595" xlink:href="mtb-20260331.xsd#mtb_InterestPaymentsOnVariableRateCommercialRealEstateLoansMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019c76d5-3dc0-771d-9c98-f69a0099edff" xlink:to="loc_mtb_InterestPaymentsOnVariableRateCommercialRealEstateLoansMember_019c76d5-3dc0-7a26-bf8a-2e54f5633595" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_019c76d5-3dc0-7f80-93b6-dd57a7ce683f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeTable_019c76d5-3dc0-715d-a34a-ba70c4582c42" xlink:to="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_019c76d5-3dc0-7f80-93b6-dd57a7ce683f" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingRelationshipDomain_019c76d5-3dc0-7f80-93b6-dd57a7ce683f_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HedgingRelationshipDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_019c76d5-3dc0-7f80-93b6-dd57a7ce683f" xlink:to="loc_us-gaap_HedgingRelationshipDomain_019c76d5-3dc0-7f80-93b6-dd57a7ce683f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingRelationshipDomain_019c76d5-3dc0-703e-b01c-db0965d7fb30" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HedgingRelationshipDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_019c76d5-3dc0-7f80-93b6-dd57a7ce683f" xlink:to="loc_us-gaap_HedgingRelationshipDomain_019c76d5-3dc0-703e-b01c-db0965d7fb30" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueHedgingMember_019c76d5-3dc0-7dfd-a553-4fad1b51edf2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueHedgingMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HedgingRelationshipDomain_019c76d5-3dc0-703e-b01c-db0965d7fb30" xlink:to="loc_us-gaap_FairValueHedgingMember_019c76d5-3dc0-7dfd-a553-4fad1b51edf2" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashFlowHedgingMember_019c76d5-3dc0-7b49-8135-fa2994248a9c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CashFlowHedgingMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HedgingRelationshipDomain_019c76d5-3dc0-703e-b01c-db0965d7fb30" xlink:to="loc_us-gaap_CashFlowHedgingMember_019c76d5-3dc0-7b49-8135-fa2994248a9c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_019c76d5-3dc0-7bb2-8971-d16c6fefc213" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeInstrumentRiskAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeTable_019c76d5-3dc0-715d-a34a-ba70c4582c42" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_019c76d5-3dc0-7bb2-8971-d16c6fefc213" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_019c76d5-3dc0-7bb2-8971-d16c6fefc213_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_019c76d5-3dc0-7bb2-8971-d16c6fefc213" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_019c76d5-3dc0-7bb2-8971-d16c6fefc213_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_019c76d5-3dc0-7c2c-af57-94e223968747" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_019c76d5-3dc0-7bb2-8971-d16c6fefc213" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_019c76d5-3dc0-7c2c-af57-94e223968747" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_ForwardStartingInterestRateSwapAgreementsMember_019c76d5-3dc0-7a76-a6b4-db2440fa9cb1" xlink:href="mtb-20260331.xsd#mtb_ForwardStartingInterestRateSwapAgreementsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_019c76d5-3dc0-7c2c-af57-94e223968747" xlink:to="loc_mtb_ForwardStartingInterestRateSwapAgreementsMember_019c76d5-3dc0-7a76-a6b4-db2440fa9cb1" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeNotionalAmount_019c76d5-3dc0-73cd-8c15-514bcee2b021" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeNotionalAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLineItems_019c76d5-3dc0-7967-9a73-b52024ad4ec9" xlink:to="loc_us-gaap_DerivativeNotionalAmount_019c76d5-3dc0-73cd-8c15-514bcee2b021" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeAverageRemainingMaturity1_019c76d5-3dc0-7ef8-9411-f38a4bfc7d49" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeAverageRemainingMaturity1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLineItems_019c76d5-3dc0-7967-9a73-b52024ad4ec9" xlink:to="loc_us-gaap_DerivativeAverageRemainingMaturity1_019c76d5-3dc0-7ef8-9411-f38a4bfc7d49" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeAverageFixedInterestRate_019c76d5-3dc0-7554-b392-7ce5e6b886e3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeAverageFixedInterestRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLineItems_019c76d5-3dc0-7967-9a73-b52024ad4ec9" xlink:to="loc_us-gaap_DerivativeAverageFixedInterestRate_019c76d5-3dc0-7554-b392-7ce5e6b886e3" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeAverageVariableInterestRate_019c76d5-3dc0-7d6a-aa89-118c180e524d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeAverageVariableInterestRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLineItems_019c76d5-3dc0-7967-9a73-b52024ad4ec9" xlink:to="loc_us-gaap_DerivativeAverageVariableInterestRate_019c76d5-3dc0-7d6a-aa89-118c180e524d" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInFairValueOfInterestRateFairValueHedgingInstruments1_019c76d5-3dc0-7e86-b0b7-55b0ad8ce173" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncreaseDecreaseInFairValueOfInterestRateFairValueHedgingInstruments1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLineItems_019c76d5-3dc0-7967-9a73-b52024ad4ec9" xlink:to="loc_us-gaap_IncreaseDecreaseInFairValueOfInterestRateFairValueHedgingInstruments1_019c76d5-3dc0-7e86-b0b7-55b0ad8ce173" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_ImpactInEstimatedFairValueGainLossesOnHedgingInstruments_019c76d5-3dc0-7d5a-abff-db71a50e90bc" xlink:href="mtb-20260331.xsd#mtb_ImpactInEstimatedFairValueGainLossesOnHedgingInstruments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLineItems_019c76d5-3dc0-7967-9a73-b52024ad4ec9" xlink:to="loc_mtb_ImpactInEstimatedFairValueGainLossesOnHedgingInstruments_019c76d5-3dc0-7d5a-abff-db71a50e90bc" xlink:type="arc" order="5"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.mtb.com/role/DerivativefinancialinstrumentsAdditionalInformationDetail" xlink:type="simple" xlink:href="mtb-20260331.xsd#DerivativefinancialinstrumentsAdditionalInformationDetail"/>
  <link:definitionLink xlink:role="http://www.mtb.com/role/DerivativefinancialinstrumentsAdditionalInformationDetail" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeLineItems_019c76d5-3dc0-73ab-81ad-eae99242a8c9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeTable_019c76d5-3dc0-7362-8008-271c1268677d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DerivativeLineItems_019c76d5-3dc0-73ab-81ad-eae99242a8c9" xlink:to="loc_us-gaap_DerivativeTable_019c76d5-3dc0-7362-8008-271c1268677d" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_019c76d5-3dc0-7b08-829e-514cdea5fe45" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeInstrumentRiskAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeTable_019c76d5-3dc0-7362-8008-271c1268677d" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_019c76d5-3dc0-7b08-829e-514cdea5fe45" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_019c76d5-3dc0-7b08-829e-514cdea5fe45_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_019c76d5-3dc0-7b08-829e-514cdea5fe45" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_019c76d5-3dc0-7b08-829e-514cdea5fe45_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_019c76d5-3dc0-73ec-88f5-767303e52af4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_019c76d5-3dc0-7b08-829e-514cdea5fe45" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_019c76d5-3dc0-73ec-88f5-767303e52af4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestRateContractMember_019c76d5-3dc0-72e5-b784-7291f7e5f708" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InterestRateContractMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_019c76d5-3dc0-73ec-88f5-767303e52af4" xlink:to="loc_us-gaap_InterestRateContractMember_019c76d5-3dc0-72e5-b784-7291f7e5f708" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_ForeignExchangeAndOtherOptionAndFuturesContractsMember_019c76d5-3dc0-7b86-a706-4c87f9771d9f" xlink:href="mtb-20260331.xsd#mtb_ForeignExchangeAndOtherOptionAndFuturesContractsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_019c76d5-3dc0-73ec-88f5-767303e52af4" xlink:to="loc_mtb_ForeignExchangeAndOtherOptionAndFuturesContractsMember_019c76d5-3dc0-7b86-a706-4c87f9771d9f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestRateSwapMember_019c76d5-3dc0-738e-ad12-30d96bb4eaa1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InterestRateSwapMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_019c76d5-3dc0-73ec-88f5-767303e52af4" xlink:to="loc_us-gaap_InterestRateSwapMember_019c76d5-3dc0-738e-ad12-30d96bb4eaa1" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationAxis_019c76d5-3dc0-7f7d-b7be-5f88fb340be7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeStatementLocationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeTable_019c76d5-3dc0-7362-8008-271c1268677d" xlink:to="loc_us-gaap_IncomeStatementLocationAxis_019c76d5-3dc0-7f7d-b7be-5f88fb340be7" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_019c76d5-3dc0-7f7d-b7be-5f88fb340be7_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeStatementLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_019c76d5-3dc0-7f7d-b7be-5f88fb340be7" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_019c76d5-3dc0-7f7d-b7be-5f88fb340be7_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_019c76d5-3dc0-7f35-88e2-29ed66b244a6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeStatementLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_019c76d5-3dc0-7f7d-b7be-5f88fb340be7" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_019c76d5-3dc0-7f35-88e2-29ed66b244a6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestIncomeMember_019c76d5-3dc0-715a-8c56-d5e74a0affdc" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InterestIncomeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_019c76d5-3dc0-7f35-88e2-29ed66b244a6" xlink:to="loc_us-gaap_InterestIncomeMember_019c76d5-3dc0-715a-8c56-d5e74a0affdc" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentRedemptionPeriodAxis_019c76d5-3dc0-7bdd-9644-2e4353b90012" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentRedemptionPeriodAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeTable_019c76d5-3dc0-7362-8008-271c1268677d" xlink:to="loc_us-gaap_DebtInstrumentRedemptionPeriodAxis_019c76d5-3dc0-7bdd-9644-2e4353b90012" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_019c76d5-3dc0-7bdd-9644-2e4353b90012_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentRedemptionPeriodDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentRedemptionPeriodAxis_019c76d5-3dc0-7bdd-9644-2e4353b90012" xlink:to="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_019c76d5-3dc0-7bdd-9644-2e4353b90012_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_019c76d5-3dc0-74ff-b6eb-4e8d0b340f03" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentRedemptionPeriodDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentRedemptionPeriodAxis_019c76d5-3dc0-7bdd-9644-2e4353b90012" xlink:to="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_019c76d5-3dc0-74ff-b6eb-4e8d0b340f03" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_MaturityPeriodTwoMember_019c76d5-3dc0-71c3-8cf5-e0ce466f1c74" xlink:href="mtb-20260331.xsd#mtb_MaturityPeriodTwoMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_019c76d5-3dc0-74ff-b6eb-4e8d0b340f03" xlink:to="loc_mtb_MaturityPeriodTwoMember_019c76d5-3dc0-71c3-8cf5-e0ce466f1c74" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentAxis_019c76d5-3dc0-7c03-848c-3a09fb810e12" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancialInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeTable_019c76d5-3dc0-7362-8008-271c1268677d" xlink:to="loc_us-gaap_FinancialInstrumentAxis_019c76d5-3dc0-7c03-848c-3a09fb810e12" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019c76d5-3dc0-7c03-848c-3a09fb810e12_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_019c76d5-3dc0-7c03-848c-3a09fb810e12" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019c76d5-3dc0-7c03-848c-3a09fb810e12_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019c76d5-3dc0-7774-bd06-4704682f0c87" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_019c76d5-3dc0-7c03-848c-3a09fb810e12" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019c76d5-3dc0-7774-bd06-4704682f0c87" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_ClearinghouseCreditFacilitiesMember_019c76d5-3dc0-789b-9247-8529f0fe1a9c" xlink:href="mtb-20260331.xsd#mtb_ClearinghouseCreditFacilitiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019c76d5-3dc0-7774-bd06-4704682f0c87" xlink:to="loc_mtb_ClearinghouseCreditFacilitiesMember_019c76d5-3dc0-789b-9247-8529f0fe1a9c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationAxis_019c76d5-3dc0-76e4-ba2c-502a4100ac72" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HedgingDesignationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeTable_019c76d5-3dc0-7362-8008-271c1268677d" xlink:to="loc_us-gaap_HedgingDesignationAxis_019c76d5-3dc0-76e4-ba2c-502a4100ac72" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationDomain_019c76d5-3dc0-76e4-ba2c-502a4100ac72_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HedgingDesignationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_HedgingDesignationAxis_019c76d5-3dc0-76e4-ba2c-502a4100ac72" xlink:to="loc_us-gaap_HedgingDesignationDomain_019c76d5-3dc0-76e4-ba2c-502a4100ac72_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationDomain_019c76d5-3dc0-7800-ae37-ae1579c931ae" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HedgingDesignationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_HedgingDesignationAxis_019c76d5-3dc0-76e4-ba2c-502a4100ac72" xlink:to="loc_us-gaap_HedgingDesignationDomain_019c76d5-3dc0-7800-ae37-ae1579c931ae" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DesignatedAsHedgingInstrumentMember_019d4e99-64ff-7908-b250-c3f523626ca5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DesignatedAsHedgingInstrumentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HedgingDesignationDomain_019c76d5-3dc0-7800-ae37-ae1579c931ae" xlink:to="loc_us-gaap_DesignatedAsHedgingInstrumentMember_019d4e99-64ff-7908-b250-c3f523626ca5" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NondesignatedMember_019c76d5-3dc0-701d-bb5f-85a24ff341d9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NondesignatedMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HedgingDesignationDomain_019c76d5-3dc0-7800-ae37-ae1579c931ae" xlink:to="loc_us-gaap_NondesignatedMember_019c76d5-3dc0-701d-bb5f-85a24ff341d9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_019c76d5-3dc0-71a7-b3ed-540d19edf2e7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeTable_019c76d5-3dc0-7362-8008-271c1268677d" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_019c76d5-3dc0-71a7-b3ed-540d19edf2e7" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_019c76d5-3dc0-71a7-b3ed-540d19edf2e7_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_019c76d5-3dc0-71a7-b3ed-540d19edf2e7" xlink:to="loc_us-gaap_EquityComponentDomain_019c76d5-3dc0-71a7-b3ed-540d19edf2e7_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_019c76d5-3dc0-7431-acb7-a792048a4580" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_019c76d5-3dc0-71a7-b3ed-540d19edf2e7" xlink:to="loc_us-gaap_EquityComponentDomain_019c76d5-3dc0-7431-acb7-a792048a4580" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedGainLossNetCashFlowHedgeParentMember_019c76d5-3dc0-7efd-a1d9-1839f8e4f122" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccumulatedGainLossNetCashFlowHedgeParentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019c76d5-3dc0-7431-acb7-a792048a4580" xlink:to="loc_us-gaap_AccumulatedGainLossNetCashFlowHedgeParentMember_019c76d5-3dc0-7efd-a1d9-1839f8e4f122" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_019d4e9a-76ec-73e8-a861-954a8ff1fb1f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeTable_019c76d5-3dc0-7362-8008-271c1268677d" xlink:to="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_019d4e9a-76ec-73e8-a861-954a8ff1fb1f" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingRelationshipDomain_019d4e9a-76ec-73e8-a861-954a8ff1fb1f_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HedgingRelationshipDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_019d4e9a-76ec-73e8-a861-954a8ff1fb1f" xlink:to="loc_us-gaap_HedgingRelationshipDomain_019d4e9a-76ec-73e8-a861-954a8ff1fb1f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingRelationshipDomain_019d4e9a-76ec-7cb6-9a8d-f6d464e3375b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HedgingRelationshipDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_019d4e9a-76ec-73e8-a861-954a8ff1fb1f" xlink:to="loc_us-gaap_HedgingRelationshipDomain_019d4e9a-76ec-7cb6-9a8d-f6d464e3375b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueHedgingMember_019d4e9a-b44b-787a-bada-f51d1c8af6b9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueHedgingMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HedgingRelationshipDomain_019d4e9a-76ec-7cb6-9a8d-f6d464e3375b" xlink:to="loc_us-gaap_FairValueHedgingMember_019d4e9a-b44b-787a-bada-f51d1c8af6b9" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeNotionalAmount_019c76d5-3dc0-7a51-9580-898063406fac" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeNotionalAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLineItems_019c76d5-3dc0-73ab-81ad-eae99242a8c9" xlink:to="loc_us-gaap_DerivativeNotionalAmount_019c76d5-3dc0-7a51-9580-898063406fac" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationBeforeTax_019c76d5-3dc0-7d6b-a76a-1668438d8ba9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationBeforeTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLineItems_019c76d5-3dc0-73ab-81ad-eae99242a8c9" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationBeforeTax_019c76d5-3dc0-7d6b-a76a-1668438d8ba9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_ChangeInCashFlowHedgesDerivativeInstrumentsAtFairValueNet_019c76d5-3dc0-7d64-8632-6616086ccb5e" xlink:href="mtb-20260331.xsd#mtb_ChangeInCashFlowHedgesDerivativeInstrumentsAtFairValueNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLineItems_019c76d5-3dc0-73ab-81ad-eae99242a8c9" xlink:to="loc_mtb_ChangeInCashFlowHedgesDerivativeInstrumentsAtFairValueNet_019c76d5-3dc0-7d64-8632-6616086ccb5e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_EquityAttributableToParentBeforeTax_019c76d5-3dc0-7ea2-a2eb-2f413440ee7d" xlink:href="mtb-20260331.xsd#mtb_EquityAttributableToParentBeforeTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLineItems_019c76d5-3dc0-73ab-81ad-eae99242a8c9" xlink:to="loc_mtb_EquityAttributableToParentBeforeTax_019c76d5-3dc0-7ea2-a2eb-2f413440ee7d" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CollateralAlreadyPostedAggregateFairValue_019c76d5-3dc0-7ab1-a48d-a4efc3cfec6c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CollateralAlreadyPostedAggregateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLineItems_019c76d5-3dc0-73ab-81ad-eae99242a8c9" xlink:to="loc_us-gaap_CollateralAlreadyPostedAggregateFairValue_019c76d5-3dc0-7ab1-a48d-a4efc3cfec6c" xlink:type="arc" order="4"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.mtb.com/role/DerivativefinancialinstrumentsInformationaboutFairValuesofDerivativeInstrumentsinConsolidatedBalanceSheetDetail" xlink:type="simple" xlink:href="mtb-20260331.xsd#DerivativefinancialinstrumentsInformationaboutFairValuesofDerivativeInstrumentsinConsolidatedBalanceSheetDetail"/>
  <link:definitionLink xlink:role="http://www.mtb.com/role/DerivativefinancialinstrumentsInformationaboutFairValuesofDerivativeInstrumentsinConsolidatedBalanceSheetDetail" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativesFairValueLineItems_019c76d5-3dc0-7df3-8bb3-03feb47d7535" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativesFairValueLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValuesDerivativesBalanceSheetLocationByDerivativeContractTypeByHedgingDesignationTable_019c76d5-3dc0-7624-8bd8-f9d5ec081560" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValuesDerivativesBalanceSheetLocationByDerivativeContractTypeByHedgingDesignationTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DerivativesFairValueLineItems_019c76d5-3dc0-7df3-8bb3-03feb47d7535" xlink:to="loc_us-gaap_FairValuesDerivativesBalanceSheetLocationByDerivativeContractTypeByHedgingDesignationTable_019c76d5-3dc0-7624-8bd8-f9d5ec081560" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_019c76d5-3dc0-7940-bec8-d6a327429412" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeInstrumentRiskAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValuesDerivativesBalanceSheetLocationByDerivativeContractTypeByHedgingDesignationTable_019c76d5-3dc0-7624-8bd8-f9d5ec081560" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_019c76d5-3dc0-7940-bec8-d6a327429412" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_019c76d5-3dc0-7940-bec8-d6a327429412_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_019c76d5-3dc0-7940-bec8-d6a327429412" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_019c76d5-3dc0-7940-bec8-d6a327429412_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_019c76d5-3dc0-7d43-a57c-aa1c42719bfb" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_019c76d5-3dc0-7940-bec8-d6a327429412" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_019c76d5-3dc0-7d43-a57c-aa1c42719bfb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestRateSwapMember_019c76d5-3dc0-7352-b4f2-43d757258da9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InterestRateSwapMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_019c76d5-3dc0-7d43-a57c-aa1c42719bfb" xlink:to="loc_us-gaap_InterestRateSwapMember_019c76d5-3dc0-7352-b4f2-43d757258da9" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_CommitmentsToSellRealEstateLoansMember_019c76d5-3dc0-7425-a779-3678495bf468" xlink:href="mtb-20260331.xsd#mtb_CommitmentsToSellRealEstateLoansMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_019c76d5-3dc0-7d43-a57c-aa1c42719bfb" xlink:to="loc_mtb_CommitmentsToSellRealEstateLoansMember_019c76d5-3dc0-7425-a779-3678495bf468" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_MortgageRelatedCommitmentsToOriginateRealEstateLoansForSaleMember_019c76d5-3dc0-7293-84d5-bfc461140654" xlink:href="mtb-20260331.xsd#mtb_MortgageRelatedCommitmentsToOriginateRealEstateLoansForSaleMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_019c76d5-3dc0-7d43-a57c-aa1c42719bfb" xlink:to="loc_mtb_MortgageRelatedCommitmentsToOriginateRealEstateLoansForSaleMember_019c76d5-3dc0-7293-84d5-bfc461140654" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_InterestRateContractForRealEstateLoansMember_019db06e-a517-7cd2-8917-0ebdd0e7ad69" xlink:href="mtb-20260331.xsd#mtb_InterestRateContractForRealEstateLoansMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_019c76d5-3dc0-7d43-a57c-aa1c42719bfb" xlink:to="loc_mtb_InterestRateContractForRealEstateLoansMember_019db06e-a517-7cd2-8917-0ebdd0e7ad69" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestRateContractMember_019c76d5-3dc0-7acc-9744-ae7c6f0d67b4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InterestRateContractMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_019c76d5-3dc0-7d43-a57c-aa1c42719bfb" xlink:to="loc_us-gaap_InterestRateContractMember_019c76d5-3dc0-7acc-9744-ae7c6f0d67b4" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_ForeignExchangeAndOtherOptionAndFuturesContractsMember_019c76d5-3dc0-7243-b845-caedc7b4f830" xlink:href="mtb-20260331.xsd#mtb_ForeignExchangeAndOtherOptionAndFuturesContractsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_019c76d5-3dc0-7d43-a57c-aa1c42719bfb" xlink:to="loc_mtb_ForeignExchangeAndOtherOptionAndFuturesContractsMember_019c76d5-3dc0-7243-b845-caedc7b4f830" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_019c76d5-3dc0-7cc4-955c-223405d2c5d1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValuesDerivativesBalanceSheetLocationByDerivativeContractTypeByHedgingDesignationTable_019c76d5-3dc0-7624-8bd8-f9d5ec081560" xlink:to="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_019c76d5-3dc0-7cc4-955c-223405d2c5d1" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingRelationshipDomain_019c76d5-3dc0-7cc4-955c-223405d2c5d1_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HedgingRelationshipDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_019c76d5-3dc0-7cc4-955c-223405d2c5d1" xlink:to="loc_us-gaap_HedgingRelationshipDomain_019c76d5-3dc0-7cc4-955c-223405d2c5d1_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingRelationshipDomain_019c76d5-3dc0-73fb-95bf-54097cce41c4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HedgingRelationshipDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_019c76d5-3dc0-7cc4-955c-223405d2c5d1" xlink:to="loc_us-gaap_HedgingRelationshipDomain_019c76d5-3dc0-73fb-95bf-54097cce41c4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueHedgingMember_019c76d5-3dc0-7f30-b729-0c7c754e23d9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueHedgingMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HedgingRelationshipDomain_019c76d5-3dc0-73fb-95bf-54097cce41c4" xlink:to="loc_us-gaap_FairValueHedgingMember_019c76d5-3dc0-7f30-b729-0c7c754e23d9" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationAxis_019c76d5-3dc0-7065-a7cd-1ce47c00aa39" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HedgingDesignationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValuesDerivativesBalanceSheetLocationByDerivativeContractTypeByHedgingDesignationTable_019c76d5-3dc0-7624-8bd8-f9d5ec081560" xlink:to="loc_us-gaap_HedgingDesignationAxis_019c76d5-3dc0-7065-a7cd-1ce47c00aa39" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationDomain_019c76d5-3dc0-7065-a7cd-1ce47c00aa39_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HedgingDesignationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_HedgingDesignationAxis_019c76d5-3dc0-7065-a7cd-1ce47c00aa39" xlink:to="loc_us-gaap_HedgingDesignationDomain_019c76d5-3dc0-7065-a7cd-1ce47c00aa39_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationDomain_019c76d5-3dc0-7a8f-b6b4-87ace2eb1d5c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HedgingDesignationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_HedgingDesignationAxis_019c76d5-3dc0-7065-a7cd-1ce47c00aa39" xlink:to="loc_us-gaap_HedgingDesignationDomain_019c76d5-3dc0-7a8f-b6b4-87ace2eb1d5c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DesignatedAsHedgingInstrumentMember_019c76d5-3dc0-717e-987c-12c4c71d0f58" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DesignatedAsHedgingInstrumentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HedgingDesignationDomain_019c76d5-3dc0-7a8f-b6b4-87ace2eb1d5c" xlink:to="loc_us-gaap_DesignatedAsHedgingInstrumentMember_019c76d5-3dc0-717e-987c-12c4c71d0f58" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NondesignatedMember_019c76d5-3dc0-76d1-8f46-16923001d10a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NondesignatedMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HedgingDesignationDomain_019c76d5-3dc0-7a8f-b6b4-87ace2eb1d5c" xlink:to="loc_us-gaap_NondesignatedMember_019c76d5-3dc0-76d1-8f46-16923001d10a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeFairValueOfDerivativeAsset_019c76d5-3dc0-7596-a7d7-fb0bf0349f8a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeFairValueOfDerivativeAsset"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativesFairValueLineItems_019c76d5-3dc0-7df3-8bb3-03feb47d7535" xlink:to="loc_us-gaap_DerivativeFairValueOfDerivativeAsset_019c76d5-3dc0-7596-a7d7-fb0bf0349f8a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeFairValueOfDerivativeLiability_019c76d5-3dc0-7bec-9dc9-79509548fe27" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeFairValueOfDerivativeLiability"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativesFairValueLineItems_019c76d5-3dc0-7df3-8bb3-03feb47d7535" xlink:to="loc_us-gaap_DerivativeFairValueOfDerivativeLiability_019c76d5-3dc0-7bec-9dc9-79509548fe27" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_IncreaseDecreaseInEstimatedFairValueOfInterestRateContractsInAssetPosition_019c76d5-3dc0-7f25-a3d8-3a8c5d609469" xlink:href="mtb-20260331.xsd#mtb_IncreaseDecreaseInEstimatedFairValueOfInterestRateContractsInAssetPosition"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativesFairValueLineItems_019c76d5-3dc0-7df3-8bb3-03feb47d7535" xlink:to="loc_mtb_IncreaseDecreaseInEstimatedFairValueOfInterestRateContractsInAssetPosition_019c76d5-3dc0-7f25-a3d8-3a8c5d609469" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_IncreaseDecreaseInEstimatedFairValueOfInterestRateContractsInLiabilityPosition_019c76d5-3dc0-7791-9a93-703dd5728666" xlink:href="mtb-20260331.xsd#mtb_IncreaseDecreaseInEstimatedFairValueOfInterestRateContractsInLiabilityPosition"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativesFairValueLineItems_019c76d5-3dc0-7df3-8bb3-03feb47d7535" xlink:to="loc_mtb_IncreaseDecreaseInEstimatedFairValueOfInterestRateContractsInLiabilityPosition_019c76d5-3dc0-7791-9a93-703dd5728666" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.mtb.com/role/DerivativefinancialinstrumentsInformationaboutFairValuesofDerivativeInstrumentsinConsolidatedStatementofIncomeDetail" xlink:type="simple" xlink:href="mtb-20260331.xsd#DerivativefinancialinstrumentsInformationaboutFairValuesofDerivativeInstrumentsinConsolidatedStatementofIncomeDetail"/>
  <link:definitionLink xlink:role="http://www.mtb.com/role/DerivativefinancialinstrumentsInformationaboutFairValuesofDerivativeInstrumentsinConsolidatedStatementofIncomeDetail" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentsGainLossLineItems_019c76d5-3dc0-7295-93d7-5e8d054e1781" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeInstrumentsGainLossLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable_019c76d5-3dc0-7007-b1aa-b3c8a0e26999" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossLineItems_019c76d5-3dc0-7295-93d7-5e8d054e1781" xlink:to="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable_019c76d5-3dc0-7007-b1aa-b3c8a0e26999" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_019c76d5-3dc0-714c-aa47-e48c84a6994e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeInstrumentRiskAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable_019c76d5-3dc0-7007-b1aa-b3c8a0e26999" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_019c76d5-3dc0-714c-aa47-e48c84a6994e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_019c76d5-3dc0-714c-aa47-e48c84a6994e_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_019c76d5-3dc0-714c-aa47-e48c84a6994e" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_019c76d5-3dc0-714c-aa47-e48c84a6994e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_019c76d5-3dc0-79f1-8771-1b9234ce1fe4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_019c76d5-3dc0-714c-aa47-e48c84a6994e" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_019c76d5-3dc0-79f1-8771-1b9234ce1fe4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestRateSwapMember_019c76d5-3dc0-7afa-9670-c378b2fcf659" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InterestRateSwapMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_019c76d5-3dc0-79f1-8771-1b9234ce1fe4" xlink:to="loc_us-gaap_InterestRateSwapMember_019c76d5-3dc0-7afa-9670-c378b2fcf659" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestRateContractMember_019c76d5-3dc0-7b05-a50e-873f4c0ec120" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InterestRateContractMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_019c76d5-3dc0-79f1-8771-1b9234ce1fe4" xlink:to="loc_us-gaap_InterestRateContractMember_019c76d5-3dc0-7b05-a50e-873f4c0ec120" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_TradingAccountAndOtherNonHedgingDerivativesMember_019df37f-cd3a-7381-a362-082b3d0aa111" xlink:href="mtb-20260331.xsd#mtb_TradingAccountAndOtherNonHedgingDerivativesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InterestRateContractMember_019c76d5-3dc0-7b05-a50e-873f4c0ec120" xlink:to="loc_mtb_TradingAccountAndOtherNonHedgingDerivativesMember_019df37f-cd3a-7381-a362-082b3d0aa111" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_MortgageBankingRevenuesMember_019df37f-fe3a-7850-a97b-8955f81d871d" xlink:href="mtb-20260331.xsd#mtb_MortgageBankingRevenuesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InterestRateContractMember_019c76d5-3dc0-7b05-a50e-873f4c0ec120" xlink:to="loc_mtb_MortgageBankingRevenuesMember_019df37f-fe3a-7850-a97b-8955f81d871d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_ForeignExchangeAndOtherOptionAndFuturesContractsMember_019c76d5-3dc0-7796-a119-95660c18e9b2" xlink:href="mtb-20260331.xsd#mtb_ForeignExchangeAndOtherOptionAndFuturesContractsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_019c76d5-3dc0-79f1-8771-1b9234ce1fe4" xlink:to="loc_mtb_ForeignExchangeAndOtherOptionAndFuturesContractsMember_019c76d5-3dc0-7796-a119-95660c18e9b2" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TradingActivityByTypeAxis_019c76d5-3dc0-78ec-9a13-4f26ef68c16f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TradingActivityByTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable_019c76d5-3dc0-7007-b1aa-b3c8a0e26999" xlink:to="loc_us-gaap_TradingActivityByTypeAxis_019c76d5-3dc0-78ec-9a13-4f26ef68c16f" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TradingActivityByTypeDomain_019c76d5-3dc0-78ec-9a13-4f26ef68c16f_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TradingActivityByTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_TradingActivityByTypeAxis_019c76d5-3dc0-78ec-9a13-4f26ef68c16f" xlink:to="loc_us-gaap_TradingActivityByTypeDomain_019c76d5-3dc0-78ec-9a13-4f26ef68c16f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TradingActivityByTypeDomain_019c76d5-3dc0-7501-9037-36912e992aab" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TradingActivityByTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_TradingActivityByTypeAxis_019c76d5-3dc0-78ec-9a13-4f26ef68c16f" xlink:to="loc_us-gaap_TradingActivityByTypeDomain_019c76d5-3dc0-7501-9037-36912e992aab" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_FixedRateLongTermBorrowingsMember_019c76d5-3dc0-79b0-96e9-0d106b6beedf" xlink:href="mtb-20260331.xsd#mtb_FixedRateLongTermBorrowingsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TradingActivityByTypeDomain_019c76d5-3dc0-7501-9037-36912e992aab" xlink:to="loc_mtb_FixedRateLongTermBorrowingsMember_019c76d5-3dc0-79b0-96e9-0d106b6beedf" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationAxis_019c76d5-3dc0-76bf-ac28-3c6e6dba3cce" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HedgingDesignationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable_019c76d5-3dc0-7007-b1aa-b3c8a0e26999" xlink:to="loc_us-gaap_HedgingDesignationAxis_019c76d5-3dc0-76bf-ac28-3c6e6dba3cce" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationDomain_019c76d5-3dc0-76bf-ac28-3c6e6dba3cce_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HedgingDesignationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_HedgingDesignationAxis_019c76d5-3dc0-76bf-ac28-3c6e6dba3cce" xlink:to="loc_us-gaap_HedgingDesignationDomain_019c76d5-3dc0-76bf-ac28-3c6e6dba3cce_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationDomain_019c76d5-3dc0-7638-b65b-cbfc01d3b941" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HedgingDesignationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_HedgingDesignationAxis_019c76d5-3dc0-76bf-ac28-3c6e6dba3cce" xlink:to="loc_us-gaap_HedgingDesignationDomain_019c76d5-3dc0-7638-b65b-cbfc01d3b941" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DesignatedAsHedgingInstrumentMember_019c76d5-3dc0-78b0-a428-d053ae20fb87" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DesignatedAsHedgingInstrumentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HedgingDesignationDomain_019c76d5-3dc0-7638-b65b-cbfc01d3b941" xlink:to="loc_us-gaap_DesignatedAsHedgingInstrumentMember_019c76d5-3dc0-78b0-a428-d053ae20fb87" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NondesignatedMember_019df37e-74e5-7bd1-a3c2-2d26a338623e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NondesignatedMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HedgingDesignationDomain_019c76d5-3dc0-7638-b65b-cbfc01d3b941" xlink:to="loc_us-gaap_NondesignatedMember_019df37e-74e5-7bd1-a3c2-2d26a338623e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_019c76d5-3dc0-7404-9b9b-dab312031541" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable_019c76d5-3dc0-7007-b1aa-b3c8a0e26999" xlink:to="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_019c76d5-3dc0-7404-9b9b-dab312031541" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingRelationshipDomain_019c76d5-3dc0-7404-9b9b-dab312031541_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HedgingRelationshipDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_019c76d5-3dc0-7404-9b9b-dab312031541" xlink:to="loc_us-gaap_HedgingRelationshipDomain_019c76d5-3dc0-7404-9b9b-dab312031541_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingRelationshipDomain_019c76d5-3dc0-7b02-9f0c-339856bc599f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HedgingRelationshipDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_019c76d5-3dc0-7404-9b9b-dab312031541" xlink:to="loc_us-gaap_HedgingRelationshipDomain_019c76d5-3dc0-7b02-9f0c-339856bc599f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueHedgingMember_019c76d5-3dc0-7bee-a0c0-0f577d08bc59" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueHedgingMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HedgingRelationshipDomain_019c76d5-3dc0-7b02-9f0c-339856bc599f" xlink:to="loc_us-gaap_FairValueHedgingMember_019c76d5-3dc0-7bee-a0c0-0f577d08bc59" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeGainLossStatementOfIncomeOrComprehensiveIncomeExtensibleEnumeration_019c76d5-3dc0-723a-b938-3420f0063cfb" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeGainLossStatementOfIncomeOrComprehensiveIncomeExtensibleEnumeration"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossLineItems_019c76d5-3dc0-7295-93d7-5e8d054e1781" xlink:to="loc_us-gaap_DerivativeGainLossStatementOfIncomeOrComprehensiveIncomeExtensibleEnumeration_019c76d5-3dc0-723a-b938-3420f0063cfb" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeGainLossOnDerivativeNet_019c76d5-3dc0-7b63-ba38-c1fae0b81014" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeGainLossOnDerivativeNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossLineItems_019c76d5-3dc0-7295-93d7-5e8d054e1781" xlink:to="loc_us-gaap_DerivativeGainLossOnDerivativeNet_019c76d5-3dc0-7b63-ba38-c1fae0b81014" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_GainLossOnHedgedItemInFairValueHedge_019c76d5-3dc0-7a80-bc1b-ea60b6f09c3f" xlink:href="mtb-20260331.xsd#mtb_GainLossOnHedgedItemInFairValueHedge"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossLineItems_019c76d5-3dc0-7295-93d7-5e8d054e1781" xlink:to="loc_mtb_GainLossOnHedgedItemInFairValueHedge_019c76d5-3dc0-7a80-bc1b-ea60b6f09c3f" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GainLossOnDerivativeInstrumentsHeldForTradingPurposesNet_019c76d5-3dc0-7053-b91d-ea4f7c54888f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_GainLossOnDerivativeInstrumentsHeldForTradingPurposesNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossLineItems_019c76d5-3dc0-7295-93d7-5e8d054e1781" xlink:to="loc_us-gaap_GainLossOnDerivativeInstrumentsHeldForTradingPurposesNet_019c76d5-3dc0-7053-b91d-ea4f7c54888f" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.mtb.com/role/DerivativefinancialinstrumentsInformationaboutHedgedItemsIncludedinConsolidatedBalanceSheetDetail" xlink:type="simple" xlink:href="mtb-20260331.xsd#DerivativefinancialinstrumentsInformationaboutHedgedItemsIncludedinConsolidatedBalanceSheetDetail"/>
  <link:definitionLink xlink:role="http://www.mtb.com/role/DerivativefinancialinstrumentsInformationaboutHedgedItemsIncludedinConsolidatedBalanceSheetDetail" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativesFairValueLineItems_019c76d5-3dc0-7be7-a670-1bc51687d80b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativesFairValueLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValuesDerivativesBalanceSheetLocationByDerivativeContractTypeByHedgingDesignationTable_019c76d5-3dc0-7387-af13-14489b597580" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValuesDerivativesBalanceSheetLocationByDerivativeContractTypeByHedgingDesignationTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DerivativesFairValueLineItems_019c76d5-3dc0-7be7-a670-1bc51687d80b" xlink:to="loc_us-gaap_FairValuesDerivativesBalanceSheetLocationByDerivativeContractTypeByHedgingDesignationTable_019c76d5-3dc0-7387-af13-14489b597580" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationAxis_019c76d5-3dc0-7917-b7a6-19b044bd3184" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HedgingDesignationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValuesDerivativesBalanceSheetLocationByDerivativeContractTypeByHedgingDesignationTable_019c76d5-3dc0-7387-af13-14489b597580" xlink:to="loc_us-gaap_HedgingDesignationAxis_019c76d5-3dc0-7917-b7a6-19b044bd3184" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationDomain_019c76d5-3dc0-7917-b7a6-19b044bd3184_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HedgingDesignationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_HedgingDesignationAxis_019c76d5-3dc0-7917-b7a6-19b044bd3184" xlink:to="loc_us-gaap_HedgingDesignationDomain_019c76d5-3dc0-7917-b7a6-19b044bd3184_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationDomain_019c76d5-3dc0-7de3-8f14-e75dcf6c3716" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HedgingDesignationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_HedgingDesignationAxis_019c76d5-3dc0-7917-b7a6-19b044bd3184" xlink:to="loc_us-gaap_HedgingDesignationDomain_019c76d5-3dc0-7de3-8f14-e75dcf6c3716" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DesignatedAsHedgingInstrumentMember_019c76d5-3dc0-7116-8d59-ede542c8e952" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DesignatedAsHedgingInstrumentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HedgingDesignationDomain_019c76d5-3dc0-7de3-8f14-e75dcf6c3716" xlink:to="loc_us-gaap_DesignatedAsHedgingInstrumentMember_019c76d5-3dc0-7116-8d59-ede542c8e952" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByMeasurementBasisAxis_019c76d5-3dc0-73b2-ba48-ffce83b499e9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueByMeasurementBasisAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValuesDerivativesBalanceSheetLocationByDerivativeContractTypeByHedgingDesignationTable_019c76d5-3dc0-7387-af13-14489b597580" xlink:to="loc_us-gaap_FairValueByMeasurementBasisAxis_019c76d5-3dc0-73b2-ba48-ffce83b499e9" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_019c76d5-3dc0-73b2-ba48-ffce83b499e9_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PortionAtFairValueFairValueDisclosureMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByMeasurementBasisAxis_019c76d5-3dc0-73b2-ba48-ffce83b499e9" xlink:to="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_019c76d5-3dc0-73b2-ba48-ffce83b499e9_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueDisclosureItemAmountsDomain_019c76d5-3dc0-7884-a49a-c5febea62270" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueDisclosureItemAmountsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByMeasurementBasisAxis_019c76d5-3dc0-73b2-ba48-ffce83b499e9" xlink:to="loc_us-gaap_FairValueDisclosureItemAmountsDomain_019c76d5-3dc0-7884-a49a-c5febea62270" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_019c76d5-3dc0-76a9-b76e-b54184c5556e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PortionAtFairValueFairValueDisclosureMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueDisclosureItemAmountsDomain_019c76d5-3dc0-7884-a49a-c5febea62270" xlink:to="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_019c76d5-3dc0-76a9-b76e-b54184c5556e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CarryingReportedAmountFairValueDisclosureMember_019c76d5-3dc0-7344-a524-8a75deefef49" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CarryingReportedAmountFairValueDisclosureMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueDisclosureItemAmountsDomain_019c76d5-3dc0-7884-a49a-c5febea62270" xlink:to="loc_us-gaap_CarryingReportedAmountFairValueDisclosureMember_019c76d5-3dc0-7344-a524-8a75deefef49" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EstimateOfFairValueFairValueDisclosureMember_019c76d5-3dc0-7a1f-a6a4-cdf99851f308" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EstimateOfFairValueFairValueDisclosureMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueDisclosureItemAmountsDomain_019c76d5-3dc0-7884-a49a-c5febea62270" xlink:to="loc_us-gaap_EstimateOfFairValueFairValueDisclosureMember_019c76d5-3dc0-7a1f-a6a4-cdf99851f308" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BalanceSheetLocationAxis_019c76d5-3dc0-7432-9f61-51c4a73e8499" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BalanceSheetLocationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValuesDerivativesBalanceSheetLocationByDerivativeContractTypeByHedgingDesignationTable_019c76d5-3dc0-7387-af13-14489b597580" xlink:to="loc_us-gaap_BalanceSheetLocationAxis_019c76d5-3dc0-7432-9f61-51c4a73e8499" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BalanceSheetLocationDomain_019c76d5-3dc0-7432-9f61-51c4a73e8499_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BalanceSheetLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BalanceSheetLocationAxis_019c76d5-3dc0-7432-9f61-51c4a73e8499" xlink:to="loc_us-gaap_BalanceSheetLocationDomain_019c76d5-3dc0-7432-9f61-51c4a73e8499_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BalanceSheetLocationDomain_019c76d5-3dc0-73d6-9649-f3d710a83024" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BalanceSheetLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BalanceSheetLocationAxis_019c76d5-3dc0-7432-9f61-51c4a73e8499" xlink:to="loc_us-gaap_BalanceSheetLocationDomain_019c76d5-3dc0-73d6-9649-f3d710a83024" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtMember_019c76d5-3dc0-7f6d-84de-5c0b5ca84912" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongTermDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BalanceSheetLocationDomain_019c76d5-3dc0-73d6-9649-f3d710a83024" xlink:to="loc_us-gaap_LongTermDebtMember_019c76d5-3dc0-7f6d-84de-5c0b5ca84912" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeAssetsLiabilitiesAtFairValueNet_019c76d5-3dc0-79ed-8cca-4e8d0d2aab74" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeAssetsLiabilitiesAtFairValueNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativesFairValueLineItems_019c76d5-3dc0-7be7-a670-1bc51687d80b" xlink:to="loc_us-gaap_DerivativeAssetsLiabilitiesAtFairValueNet_019c76d5-3dc0-79ed-8cca-4e8d0d2aab74" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.mtb.com/role/DerivativeFinancialInstrumentsScheduleofFairValuewithNettingDetails" xlink:type="simple" xlink:href="mtb-20260331.xsd#DerivativeFinancialInstrumentsScheduleofFairValuewithNettingDetails"/>
  <link:definitionLink xlink:role="http://www.mtb.com/role/DerivativeFinancialInstrumentsScheduleofFairValuewithNettingDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeLineItems_019d49b0-d464-78c5-a8f3-0720e51d2bf7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeTable_019d49b0-d464-7112-8610-dfe4358d875e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DerivativeLineItems_019d49b0-d464-78c5-a8f3-0720e51d2bf7" xlink:to="loc_us-gaap_DerivativeTable_019d49b0-d464-7112-8610-dfe4358d875e" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransactionTypeAxis_019d49b0-d464-769e-9d2e-0d5d597d0729" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TransactionTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeTable_019d49b0-d464-7112-8610-dfe4358d875e" xlink:to="loc_us-gaap_TransactionTypeAxis_019d49b0-d464-769e-9d2e-0d5d597d0729" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransactionDomain_019d49b0-d464-769e-9d2e-0d5d597d0729_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TransactionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_TransactionTypeAxis_019d49b0-d464-769e-9d2e-0d5d597d0729" xlink:to="loc_us-gaap_TransactionDomain_019d49b0-d464-769e-9d2e-0d5d597d0729_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransactionDomain_019d49b0-d464-7da7-a90d-ea0be7d1aed2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TransactionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_TransactionTypeAxis_019d49b0-d464-769e-9d2e-0d5d597d0729" xlink:to="loc_us-gaap_TransactionDomain_019d49b0-d464-7da7-a90d-ea0be7d1aed2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ExchangeClearedMember_019d49b0-d464-7c43-87e9-f5eddce186e1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ExchangeClearedMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransactionDomain_019d49b0-d464-7da7-a90d-ea0be7d1aed2" xlink:to="loc_us-gaap_ExchangeClearedMember_019d49b0-d464-7c43-87e9-f5eddce186e1" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OverTheCounterMember_019d49b0-d464-7922-bb98-13bfc0501c11" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OverTheCounterMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransactionDomain_019d49b0-d464-7da7-a90d-ea0be7d1aed2" xlink:to="loc_us-gaap_OverTheCounterMember_019d49b0-d464-7922-bb98-13bfc0501c11" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OffsettingDerivativeAssetsAbstract_019d49b1-2803-7304-b8a9-efeddcab531b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OffsettingDerivativeAssetsAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLineItems_019d49b0-d464-78c5-a8f3-0720e51d2bf7" xlink:to="loc_us-gaap_OffsettingDerivativeAssetsAbstract_019d49b1-2803-7304-b8a9-efeddcab531b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeFairValueOfDerivativeAsset_019d49b0-d464-749f-998e-6b5ee77eba7c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeFairValueOfDerivativeAsset"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OffsettingDerivativeAssetsAbstract_019d49b1-2803-7304-b8a9-efeddcab531b" xlink:to="loc_us-gaap_DerivativeFairValueOfDerivativeAsset_019d49b0-d464-749f-998e-6b5ee77eba7c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeAssetFairValueGrossLiability_019d49b0-d464-7796-aa9c-452d9be0a8aa" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeAssetFairValueGrossLiability"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OffsettingDerivativeAssetsAbstract_019d49b1-2803-7304-b8a9-efeddcab531b" xlink:to="loc_us-gaap_DerivativeAssetFairValueGrossLiability_019d49b0-d464-7796-aa9c-452d9be0a8aa" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeAssetCollateralObligationToReturnCashOffset_019d49b0-d464-7f79-abad-518d0f427c62" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeAssetCollateralObligationToReturnCashOffset"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OffsettingDerivativeAssetsAbstract_019d49b1-2803-7304-b8a9-efeddcab531b" xlink:to="loc_us-gaap_DerivativeAssetCollateralObligationToReturnCashOffset_019d49b0-d464-7f79-abad-518d0f427c62" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeAssetFairValueAfterOffsetAndDeductionSubjectToMasterNettingArrangement_019d49b0-d464-7f2b-8c95-8366d1b09567" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeAssetFairValueAfterOffsetAndDeductionSubjectToMasterNettingArrangement"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OffsettingDerivativeAssetsAbstract_019d49b1-2803-7304-b8a9-efeddcab531b" xlink:to="loc_us-gaap_DerivativeAssetFairValueAfterOffsetAndDeductionSubjectToMasterNettingArrangement_019d49b0-d464-7f2b-8c95-8366d1b09567" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeAssetNotSubjectToMasterNettingArrangement_019d49b0-d464-7302-ab8f-7da0f1ad6bde" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeAssetNotSubjectToMasterNettingArrangement"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OffsettingDerivativeAssetsAbstract_019d49b1-2803-7304-b8a9-efeddcab531b" xlink:to="loc_us-gaap_DerivativeAssetNotSubjectToMasterNettingArrangement_019d49b0-d464-7302-ab8f-7da0f1ad6bde" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_DerivativeAssetNotSubjectToMasterNettingArrangementCollateralRightToReclaimCashOffset_019db05e-ca94-7750-9b34-0e4b027a2acc" xlink:href="mtb-20260331.xsd#mtb_DerivativeAssetNotSubjectToMasterNettingArrangementCollateralRightToReclaimCashOffset"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OffsettingDerivativeAssetsAbstract_019d49b1-2803-7304-b8a9-efeddcab531b" xlink:to="loc_mtb_DerivativeAssetNotSubjectToMasterNettingArrangementCollateralRightToReclaimCashOffset_019db05e-ca94-7750-9b34-0e4b027a2acc" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_DerivativeAssetNotSubjectToMasterNettingArrangementAfterOffset_019db05f-7da4-785c-a4aa-05e7b2500ba0" xlink:href="mtb-20260331.xsd#mtb_DerivativeAssetNotSubjectToMasterNettingArrangementAfterOffset"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OffsettingDerivativeAssetsAbstract_019d49b1-2803-7304-b8a9-efeddcab531b" xlink:to="loc_mtb_DerivativeAssetNotSubjectToMasterNettingArrangementAfterOffset_019db05f-7da4-785c-a4aa-05e7b2500ba0" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeAssets_019d49b0-d464-7005-8468-30ac65477779" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OffsettingDerivativeAssetsAbstract_019d49b1-2803-7304-b8a9-efeddcab531b" xlink:to="loc_us-gaap_DerivativeAssets_019d49b0-d464-7005-8468-30ac65477779" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeAssetFairValueGrossAssetIncludingNotSubjectToMasterNettingArrangement_019d49b0-d464-7b98-8774-5d43fa4f361b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeAssetFairValueGrossAssetIncludingNotSubjectToMasterNettingArrangement"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OffsettingDerivativeAssetsAbstract_019d49b1-2803-7304-b8a9-efeddcab531b" xlink:to="loc_us-gaap_DerivativeAssetFairValueGrossAssetIncludingNotSubjectToMasterNettingArrangement_019d49b0-d464-7b98-8774-5d43fa4f361b" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OffsettingDerivativeLiabilitiesAbstract_019d49b4-a560-7d23-b21a-a795d7a2a18a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OffsettingDerivativeLiabilitiesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLineItems_019d49b0-d464-78c5-a8f3-0720e51d2bf7" xlink:to="loc_us-gaap_OffsettingDerivativeLiabilitiesAbstract_019d49b4-a560-7d23-b21a-a795d7a2a18a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeFairValueOfDerivativeLiability_019d49b0-d464-783c-ae32-e56c223aa2ce" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeFairValueOfDerivativeLiability"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OffsettingDerivativeLiabilitiesAbstract_019d49b4-a560-7d23-b21a-a795d7a2a18a" xlink:to="loc_us-gaap_DerivativeFairValueOfDerivativeLiability_019d49b0-d464-783c-ae32-e56c223aa2ce" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeLiabilityFairValueGrossAsset_019d49b0-d464-70bd-ac95-644f288fc059" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeLiabilityFairValueGrossAsset"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OffsettingDerivativeLiabilitiesAbstract_019d49b4-a560-7d23-b21a-a795d7a2a18a" xlink:to="loc_us-gaap_DerivativeLiabilityFairValueGrossAsset_019d49b0-d464-70bd-ac95-644f288fc059" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeLiabilityCollateralRightToReclaimCashOffset_019d49b0-d464-790d-9dc6-7494eacc7af6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeLiabilityCollateralRightToReclaimCashOffset"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OffsettingDerivativeLiabilitiesAbstract_019d49b4-a560-7d23-b21a-a795d7a2a18a" xlink:to="loc_us-gaap_DerivativeLiabilityCollateralRightToReclaimCashOffset_019d49b0-d464-790d-9dc6-7494eacc7af6" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeLiabilityFairValueAfterOffsetAndDeductionSubjectToMasterNettingArrangement_019d49b0-d464-7fe6-889f-0ca5c769f746" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeLiabilityFairValueAfterOffsetAndDeductionSubjectToMasterNettingArrangement"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OffsettingDerivativeLiabilitiesAbstract_019d49b4-a560-7d23-b21a-a795d7a2a18a" xlink:to="loc_us-gaap_DerivativeLiabilityFairValueAfterOffsetAndDeductionSubjectToMasterNettingArrangement_019d49b0-d464-7fe6-889f-0ca5c769f746" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeLiabilityNotSubjectToMasterNettingArrangement_019d49b0-d464-7f8a-96ba-a48e851b268f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeLiabilityNotSubjectToMasterNettingArrangement"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OffsettingDerivativeLiabilitiesAbstract_019d49b4-a560-7d23-b21a-a795d7a2a18a" xlink:to="loc_us-gaap_DerivativeLiabilityNotSubjectToMasterNettingArrangement_019d49b0-d464-7f8a-96ba-a48e851b268f" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_DerivativeLiabilityNotSubjectToMasterNettingArrangementCollateralRightToReclaimCashOffset_019d49b0-d464-741f-89df-64a28bbb8741" xlink:href="mtb-20260331.xsd#mtb_DerivativeLiabilityNotSubjectToMasterNettingArrangementCollateralRightToReclaimCashOffset"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OffsettingDerivativeLiabilitiesAbstract_019d49b4-a560-7d23-b21a-a795d7a2a18a" xlink:to="loc_mtb_DerivativeLiabilityNotSubjectToMasterNettingArrangementCollateralRightToReclaimCashOffset_019d49b0-d464-741f-89df-64a28bbb8741" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_DerivativeLiabilityNotSubjectToMasterNettingArrangementAfterOffset_019d49b0-d464-7977-98b3-b987e207c97a" xlink:href="mtb-20260331.xsd#mtb_DerivativeLiabilityNotSubjectToMasterNettingArrangementAfterOffset"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OffsettingDerivativeLiabilitiesAbstract_019d49b4-a560-7d23-b21a-a795d7a2a18a" xlink:to="loc_mtb_DerivativeLiabilityNotSubjectToMasterNettingArrangementAfterOffset_019d49b0-d464-7977-98b3-b987e207c97a" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeLiabilities_019d49b0-d464-7df4-ae88-8e7830ae0cc7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeLiabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OffsettingDerivativeLiabilitiesAbstract_019d49b4-a560-7d23-b21a-a795d7a2a18a" xlink:to="loc_us-gaap_DerivativeLiabilities_019d49b0-d464-7df4-ae88-8e7830ae0cc7" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeLiabilityFairValueGrossLiabilityIncludingNotSubjectToMasterNettingArrangement_019d49b0-d464-73df-a815-7d2cc15aec2b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeLiabilityFairValueGrossLiabilityIncludingNotSubjectToMasterNettingArrangement"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OffsettingDerivativeLiabilitiesAbstract_019d49b4-a560-7d23-b21a-a795d7a2a18a" xlink:to="loc_us-gaap_DerivativeLiabilityFairValueGrossLiabilityIncludingNotSubjectToMasterNettingArrangement_019d49b0-d464-73df-a815-7d2cc15aec2b" xlink:type="arc" order="9"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.mtb.com/role/VariableinterestentitiesandassetsecuritizationsAssetbackedNotesIssuedtoInvestorsDetails" xlink:type="simple" xlink:href="mtb-20260331.xsd#VariableinterestentitiesandassetsecuritizationsAssetbackedNotesIssuedtoInvestorsDetails"/>
  <link:definitionLink xlink:role="http://www.mtb.com/role/VariableinterestentitiesandassetsecuritizationsAssetbackedNotesIssuedtoInvestorsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableInterestEntityLineItems_019c76d5-3dc0-737e-ae9c-a05df09a5b42" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_VariableInterestEntityLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfVariableInterestEntitiesTable_019c76d5-3dc0-795d-9d14-1f7cb08a9a9a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfVariableInterestEntitiesTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_VariableInterestEntityLineItems_019c76d5-3dc0-737e-ae9c-a05df09a5b42" xlink:to="loc_us-gaap_ScheduleOfVariableInterestEntitiesTable_019c76d5-3dc0-795d-9d14-1f7cb08a9a9a" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_019c76d5-3dc0-7496-aa3a-32c180c48cca" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfVariableInterestEntitiesTable_019c76d5-3dc0-795d-9d14-1f7cb08a9a9a" xlink:to="loc_us-gaap_DebtInstrumentAxis_019c76d5-3dc0-7496-aa3a-32c180c48cca" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_019c76d5-3dc0-7496-aa3a-32c180c48cca_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_019c76d5-3dc0-7496-aa3a-32c180c48cca" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_019c76d5-3dc0-7496-aa3a-32c180c48cca_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_019c76d5-3dc0-7ed2-8a32-03bc99b2b606" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_019c76d5-3dc0-7496-aa3a-32c180c48cca" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_019c76d5-3dc0-7ed2-8a32-03bc99b2b606" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_AssetBackedNotesAugust2023Member_019c76d5-3dc0-767b-b65a-771c932fb749" xlink:href="mtb-20260331.xsd#mtb_AssetBackedNotesAugust2023Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019c76d5-3dc0-7ed2-8a32-03bc99b2b606" xlink:to="loc_mtb_AssetBackedNotesAugust2023Member_019c76d5-3dc0-767b-b65a-771c932fb749" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_AssetBackedNotesMarch2024Member_019c76d5-3dc0-7272-a448-d45164059030" xlink:href="mtb-20260331.xsd#mtb_AssetBackedNotesMarch2024Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019c76d5-3dc0-7ed2-8a32-03bc99b2b606" xlink:to="loc_mtb_AssetBackedNotesMarch2024Member_019c76d5-3dc0-7272-a448-d45164059030" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_AssetBackedNotesAugust2024Member_019c76d5-3dc0-708e-be8f-09715a1bb118" xlink:href="mtb-20260331.xsd#mtb_AssetBackedNotesAugust2024Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019c76d5-3dc0-7ed2-8a32-03bc99b2b606" xlink:to="loc_mtb_AssetBackedNotesAugust2024Member_019c76d5-3dc0-708e-be8f-09715a1bb118" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_AssetBackedNotesFebruary2025Member_019c76d5-3dc0-7948-8a35-7887c3554325" xlink:href="mtb-20260331.xsd#mtb_AssetBackedNotesFebruary2025Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019c76d5-3dc0-7ed2-8a32-03bc99b2b606" xlink:to="loc_mtb_AssetBackedNotesFebruary2025Member_019c76d5-3dc0-7948-8a35-7887c3554325" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_AssetBackedNotesMay2025Member_019c76d5-3dc0-7bbb-9a34-f81a5766c109" xlink:href="mtb-20260331.xsd#mtb_AssetBackedNotesMay2025Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019c76d5-3dc0-7ed2-8a32-03bc99b2b606" xlink:to="loc_mtb_AssetBackedNotesMay2025Member_019c76d5-3dc0-7bbb-9a34-f81a5766c109" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_AssetBackedNotesFebruary2026Member_019d49bb-3f63-7886-8853-793fd7e1521f" xlink:href="mtb-20260331.xsd#mtb_AssetBackedNotesFebruary2026Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019c76d5-3dc0-7ed2-8a32-03bc99b2b606" xlink:to="loc_mtb_AssetBackedNotesFebruary2026Member_019d49bb-3f63-7886-8853-793fd7e1521f" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CollateralAxis_019c76d5-3dc0-718e-b4a7-2bc47c46bdf7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CollateralAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfVariableInterestEntitiesTable_019c76d5-3dc0-795d-9d14-1f7cb08a9a9a" xlink:to="loc_us-gaap_CollateralAxis_019c76d5-3dc0-718e-b4a7-2bc47c46bdf7" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CollateralDomain_019c76d5-3dc0-718e-b4a7-2bc47c46bdf7_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CollateralDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CollateralAxis_019c76d5-3dc0-718e-b4a7-2bc47c46bdf7" xlink:to="loc_us-gaap_CollateralDomain_019c76d5-3dc0-718e-b4a7-2bc47c46bdf7_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CollateralDomain_019c76d5-3dc0-74ff-b8dd-f883858f0d7f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CollateralDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CollateralAxis_019c76d5-3dc0-718e-b4a7-2bc47c46bdf7" xlink:to="loc_us-gaap_CollateralDomain_019c76d5-3dc0-74ff-b8dd-f883858f0d7f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_EquipmentFinanceLoansAndLeasesMember_019c76d5-3dc0-744d-8e68-5287d584fc8e" xlink:href="mtb-20260331.xsd#mtb_EquipmentFinanceLoansAndLeasesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CollateralDomain_019c76d5-3dc0-74ff-b8dd-f883858f0d7f" xlink:to="loc_mtb_EquipmentFinanceLoansAndLeasesMember_019c76d5-3dc0-744d-8e68-5287d584fc8e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_AutomobileLoansMember_019c76d5-3dc0-72d9-a2da-c88ab86a12f5" xlink:href="mtb-20260331.xsd#mtb_AutomobileLoansMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CollateralDomain_019c76d5-3dc0-74ff-b8dd-f883858f0d7f" xlink:to="loc_mtb_AutomobileLoansMember_019c76d5-3dc0-72d9-a2da-c88ab86a12f5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_RecreationalFinanceLoansMember_019d49bb-dab6-7512-8703-d6f981ddc5b9" xlink:href="mtb-20260331.xsd#mtb_RecreationalFinanceLoansMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CollateralDomain_019c76d5-3dc0-74ff-b8dd-f883858f0d7f" xlink:to="loc_mtb_RecreationalFinanceLoansMember_019d49bb-dab6-7512-8703-d6f981ddc5b9" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentCollateralAmount_019c76d5-3dc0-79f6-b67f-1b716b76c849" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentCollateralAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableInterestEntityLineItems_019c76d5-3dc0-737e-ae9c-a05df09a5b42" xlink:to="loc_us-gaap_DebtInstrumentCollateralAmount_019c76d5-3dc0-79f6-b67f-1b716b76c849" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentFaceAmount_019c76d5-3dc0-7a5b-b9a3-ec9924fa9eb6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentFaceAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableInterestEntityLineItems_019c76d5-3dc0-737e-ae9c-a05df09a5b42" xlink:to="loc_us-gaap_DebtInstrumentFaceAmount_019c76d5-3dc0-7a5b-b9a3-ec9924fa9eb6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTerm_019c76d5-3dc0-761b-92e6-4fa9d95f8359" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentTerm"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableInterestEntityLineItems_019c76d5-3dc0-737e-ae9c-a05df09a5b42" xlink:to="loc_us-gaap_DebtInstrumentTerm_019c76d5-3dc0-761b-92e6-4fa9d95f8359" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtWeightedAverageInterestRate_019c76d5-3dc0-71da-a3ab-16fa57950241" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtWeightedAverageInterestRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableInterestEntityLineItems_019c76d5-3dc0-737e-ae9c-a05df09a5b42" xlink:to="loc_us-gaap_DebtWeightedAverageInterestRate_019c76d5-3dc0-71da-a3ab-16fa57950241" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.mtb.com/role/VariableinterestentitiesandassetsecuritizationsAdditionalInformationDetail" xlink:type="simple" xlink:href="mtb-20260331.xsd#VariableinterestentitiesandassetsecuritizationsAdditionalInformationDetail"/>
  <link:definitionLink xlink:role="http://www.mtb.com/role/VariableinterestentitiesandassetsecuritizationsAdditionalInformationDetail" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_019c76d5-3dc0-79a3-b823-6c971936340e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfVariableInterestEntitiesTable_019c76d5-3dc0-761b-8120-90098eddc18e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfVariableInterestEntitiesTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_019c76d5-3dc0-79a3-b823-6c971936340e" xlink:to="loc_us-gaap_ScheduleOfVariableInterestEntitiesTable_019c76d5-3dc0-761b-8120-90098eddc18e" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesAxis_019c76d5-3dc0-7e62-8d79-17794e439ee7" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ConsolidatedEntitiesAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfVariableInterestEntitiesTable_019c76d5-3dc0-761b-8120-90098eddc18e" xlink:to="loc_srt_ConsolidatedEntitiesAxis_019c76d5-3dc0-7e62-8d79-17794e439ee7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_019c76d5-3dc0-7e62-8d79-17794e439ee7_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidatedEntitiesAxis_019c76d5-3dc0-7e62-8d79-17794e439ee7" xlink:to="loc_srt_ConsolidatedEntitiesDomain_019c76d5-3dc0-7e62-8d79-17794e439ee7_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_019c76d5-3dc0-7e68-a8af-f49285a4a0ee" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidatedEntitiesAxis_019c76d5-3dc0-7e62-8d79-17794e439ee7" xlink:to="loc_srt_ConsolidatedEntitiesDomain_019c76d5-3dc0-7e68-a8af-f49285a4a0ee" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableInterestEntityPrimaryBeneficiaryMember_019c76d5-3dc0-77b8-8af6-052ecbb7c377" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_VariableInterestEntityPrimaryBeneficiaryMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidatedEntitiesDomain_019c76d5-3dc0-7e68-a8af-f49285a4a0ee" xlink:to="loc_us-gaap_VariableInterestEntityPrimaryBeneficiaryMember_019c76d5-3dc0-77b8-8af6-052ecbb7c377" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentTypeAxis_019c76d5-3dc0-7c1b-ab12-7161a425dfe4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InvestmentTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfVariableInterestEntitiesTable_019c76d5-3dc0-761b-8120-90098eddc18e" xlink:to="loc_us-gaap_InvestmentTypeAxis_019c76d5-3dc0-7c1b-ab12-7161a425dfe4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentTypeCategorizationMember_019c76d5-3dc0-7c1b-ab12-7161a425dfe4_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InvestmentTypeCategorizationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_InvestmentTypeAxis_019c76d5-3dc0-7c1b-ab12-7161a425dfe4" xlink:to="loc_us-gaap_InvestmentTypeCategorizationMember_019c76d5-3dc0-7c1b-ab12-7161a425dfe4_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentTypeCategorizationMember_019c76d5-3dc0-7a83-a8ae-fd8113aa89c1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InvestmentTypeCategorizationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_InvestmentTypeAxis_019c76d5-3dc0-7c1b-ab12-7161a425dfe4" xlink:to="loc_us-gaap_InvestmentTypeCategorizationMember_019c76d5-3dc0-7a83-a8ae-fd8113aa89c1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_RenewableEnergyMember_019c76d5-3dc0-7dba-822c-45988632d55a" xlink:href="mtb-20260331.xsd#mtb_RenewableEnergyMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InvestmentTypeCategorizationMember_019c76d5-3dc0-7a83-a8ae-fd8113aa89c1" xlink:to="loc_mtb_RenewableEnergyMember_019c76d5-3dc0-7dba-822c-45988632d55a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_OtherAssetsForItsInvestmentInCommonSecuritiesRecognizedByCompanyOfVariousTrusts_019c76d5-3dc0-7d57-b1b7-99be2a301eae" xlink:href="mtb-20260331.xsd#mtb_OtherAssetsForItsInvestmentInCommonSecuritiesRecognizedByCompanyOfVariousTrusts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019c76d5-3dc0-79a3-b823-6c971936340e" xlink:to="loc_mtb_OtherAssetsForItsInvestmentInCommonSecuritiesRecognizedByCompanyOfVariousTrusts_019c76d5-3dc0-7d57-b1b7-99be2a301eae" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Assets_019c76d5-3dc0-7e00-9653-f4f24f2d6599" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_Assets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019c76d5-3dc0-79a3-b823-6c971936340e" xlink:to="loc_us-gaap_Assets_019c76d5-3dc0-7e00-9653-f4f24f2d6599" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AffordableHousingTaxCreditsAndOtherTaxBenefitsAmount_019c76d5-3dc0-7988-9d60-0b3c0e9fa3d3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AffordableHousingTaxCreditsAndOtherTaxBenefitsAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019c76d5-3dc0-79a3-b823-6c971936340e" xlink:to="loc_us-gaap_AffordableHousingTaxCreditsAndOtherTaxBenefitsAmount_019c76d5-3dc0-7988-9d60-0b3c0e9fa3d3" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AmortizationMethodQualifiedAffordableHousingProjectInvestmentsAmortization_019c76d5-3dc0-7d74-a6a9-91b5ef356991" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AmortizationMethodQualifiedAffordableHousingProjectInvestmentsAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019c76d5-3dc0-79a3-b823-6c971936340e" xlink:to="loc_us-gaap_AmortizationMethodQualifiedAffordableHousingProjectInvestmentsAmortization_019c76d5-3dc0-7d74-a6a9-91b5ef356991" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_MaximumExposureToLossOfInvestmentsInRealEstatePartnerships_019c76d5-3dc0-7ff2-8c02-34e046815784" xlink:href="mtb-20260331.xsd#mtb_MaximumExposureToLossOfInvestmentsInRealEstatePartnerships"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019c76d5-3dc0-79a3-b823-6c971936340e" xlink:to="loc_mtb_MaximumExposureToLossOfInvestmentsInRealEstatePartnerships_019c76d5-3dc0-7ff2-8c02-34e046815784" xlink:type="arc" order="4"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.mtb.com/role/VariableinterestentitiesandassetsecuritizationsSummaryofCarryingAmountDetails" xlink:type="simple" xlink:href="mtb-20260331.xsd#VariableinterestentitiesandassetsecuritizationsSummaryofCarryingAmountDetails"/>
  <link:definitionLink xlink:role="http://www.mtb.com/role/VariableinterestentitiesandassetsecuritizationsSummaryofCarryingAmountDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableInterestEntityLineItems_019c76d5-3dc0-7fd9-afe8-2157b7aa8d88" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_VariableInterestEntityLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfVariableInterestEntitiesTable_019c76d5-3dc0-78b6-9185-23b5af3a8bd5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfVariableInterestEntitiesTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_VariableInterestEntityLineItems_019c76d5-3dc0-7fd9-afe8-2157b7aa8d88" xlink:to="loc_us-gaap_ScheduleOfVariableInterestEntitiesTable_019c76d5-3dc0-78b6-9185-23b5af3a8bd5" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesAxis_019c76d5-3dc0-7113-a2c3-c7774e68fd0d" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ConsolidatedEntitiesAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfVariableInterestEntitiesTable_019c76d5-3dc0-78b6-9185-23b5af3a8bd5" xlink:to="loc_srt_ConsolidatedEntitiesAxis_019c76d5-3dc0-7113-a2c3-c7774e68fd0d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_019c76d5-3dc0-7113-a2c3-c7774e68fd0d_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidatedEntitiesAxis_019c76d5-3dc0-7113-a2c3-c7774e68fd0d" xlink:to="loc_srt_ConsolidatedEntitiesDomain_019c76d5-3dc0-7113-a2c3-c7774e68fd0d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_019c76d5-3dc0-7b6e-9fc1-b0c7c2ee97c2" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidatedEntitiesAxis_019c76d5-3dc0-7113-a2c3-c7774e68fd0d" xlink:to="loc_srt_ConsolidatedEntitiesDomain_019c76d5-3dc0-7b6e-9fc1-b0c7c2ee97c2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableInterestEntityPrimaryBeneficiaryMember_019c76d5-3dc0-72da-9ecb-564f7e3adf37" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_VariableInterestEntityPrimaryBeneficiaryMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidatedEntitiesDomain_019c76d5-3dc0-7b6e-9fc1-b0c7c2ee97c2" xlink:to="loc_us-gaap_VariableInterestEntityPrimaryBeneficiaryMember_019c76d5-3dc0-72da-9ecb-564f7e3adf37" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherCommitmentsAxis_019c76d5-3dc0-75ff-aea5-4ae501650542" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherCommitmentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfVariableInterestEntitiesTable_019c76d5-3dc0-78b6-9185-23b5af3a8bd5" xlink:to="loc_us-gaap_OtherCommitmentsAxis_019c76d5-3dc0-75ff-aea5-4ae501650542" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherCommitmentsDomain_019c76d5-3dc0-75ff-aea5-4ae501650542_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherCommitmentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_OtherCommitmentsAxis_019c76d5-3dc0-75ff-aea5-4ae501650542" xlink:to="loc_us-gaap_OtherCommitmentsDomain_019c76d5-3dc0-75ff-aea5-4ae501650542_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherCommitmentsDomain_019c76d5-3dc0-74f0-83e8-bd4b33dcf492" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherCommitmentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_OtherCommitmentsAxis_019c76d5-3dc0-75ff-aea5-4ae501650542" xlink:to="loc_us-gaap_OtherCommitmentsDomain_019c76d5-3dc0-74f0-83e8-bd4b33dcf492" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_AffordableHousingProjectsMember_019c76d5-3dc0-7c0e-9ce6-eef23b2d87cc" xlink:href="mtb-20260331.xsd#mtb_AffordableHousingProjectsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherCommitmentsDomain_019c76d5-3dc0-74f0-83e8-bd4b33dcf492" xlink:to="loc_mtb_AffordableHousingProjectsMember_019c76d5-3dc0-7c0e-9ce6-eef23b2d87cc" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_RenewableEnergyMember_019c76d5-3dc0-72a3-a3a8-673e39caecb4" xlink:href="mtb-20260331.xsd#mtb_RenewableEnergyMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherCommitmentsDomain_019c76d5-3dc0-74f0-83e8-bd4b33dcf492" xlink:to="loc_mtb_RenewableEnergyMember_019c76d5-3dc0-72a3-a3a8-673e39caecb4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_OtherProjectsMember_019c76d5-3dc0-73bd-aca9-b89d051df72a" xlink:href="mtb-20260331.xsd#mtb_OtherProjectsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherCommitmentsDomain_019c76d5-3dc0-74f0-83e8-bd4b33dcf492" xlink:to="loc_mtb_OtherProjectsMember_019c76d5-3dc0-73bd-aca9-b89d051df72a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_InvestmentsInVariableInterestEntityCarryingAmount_019c76d5-3dc0-7aa6-8f54-1bdad59e49a9" xlink:href="mtb-20260331.xsd#mtb_InvestmentsInVariableInterestEntityCarryingAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableInterestEntityLineItems_019c76d5-3dc0-7fd9-afe8-2157b7aa8d88" xlink:to="loc_mtb_InvestmentsInVariableInterestEntityCarryingAmount_019c76d5-3dc0-7aa6-8f54-1bdad59e49a9" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_UnfundedCommitmentsIncludesCarryingAmountOfItsInvestments_019c76d5-3dc0-7664-a89b-f81d015e3b67" xlink:href="mtb-20260331.xsd#mtb_UnfundedCommitmentsIncludesCarryingAmountOfItsInvestments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableInterestEntityLineItems_019c76d5-3dc0-7fd9-afe8-2157b7aa8d88" xlink:to="loc_mtb_UnfundedCommitmentsIncludesCarryingAmountOfItsInvestments_019c76d5-3dc0-7664-a89b-f81d015e3b67" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_ContingentCommitmentsToProvideAdditionalCapitalContributionsToPartnerships_019c76d5-3dc0-75b4-aac6-1687b77afd48" xlink:href="mtb-20260331.xsd#mtb_ContingentCommitmentsToProvideAdditionalCapitalContributionsToPartnerships"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableInterestEntityLineItems_019c76d5-3dc0-7fd9-afe8-2157b7aa8d88" xlink:to="loc_mtb_ContingentCommitmentsToProvideAdditionalCapitalContributionsToPartnerships_019c76d5-3dc0-75b4-aac6-1687b77afd48" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.mtb.com/role/FairvaluemeasurementsAssetsandLiabilitiesMeasuredatEstimatedFairValueonRecurringBasisDetail" xlink:type="simple" xlink:href="mtb-20260331.xsd#FairvaluemeasurementsAssetsandLiabilitiesMeasuredatEstimatedFairValueonRecurringBasisDetail"/>
  <link:definitionLink xlink:role="http://www.mtb.com/role/FairvaluemeasurementsAssetsandLiabilitiesMeasuredatEstimatedFairValueonRecurringBasisDetail" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019c76d5-3dc0-711e-b7db-f692a5add711" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_019c76d5-3dc0-7ad1-887d-3a9b763660bc" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019c76d5-3dc0-711e-b7db-f692a5add711" xlink:to="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_019c76d5-3dc0-7ad1-887d-3a9b763660bc" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019c76d5-3dc0-785f-b7f1-92fbe9eadd43" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_019c76d5-3dc0-7ad1-887d-3a9b763660bc" xlink:to="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019c76d5-3dc0-785f-b7f1-92fbe9eadd43" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019c76d5-3dc0-785f-b7f1-92fbe9eadd43_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019c76d5-3dc0-785f-b7f1-92fbe9eadd43" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019c76d5-3dc0-785f-b7f1-92fbe9eadd43_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019c76d5-3dc0-79d4-a960-fb451c58747b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019c76d5-3dc0-785f-b7f1-92fbe9eadd43" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019c76d5-3dc0-79d4-a960-fb451c58747b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel12And3Member_019c76d5-3dc0-7ed2-ace9-2efbe6df4000" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueInputsLevel12And3Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019c76d5-3dc0-79d4-a960-fb451c58747b" xlink:to="loc_us-gaap_FairValueInputsLevel12And3Member_019c76d5-3dc0-7ed2-ace9-2efbe6df4000" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel1Member_019c76d5-3dc0-7e15-94a2-2f09d0707684" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueInputsLevel1Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueInputsLevel12And3Member_019c76d5-3dc0-7ed2-ace9-2efbe6df4000" xlink:to="loc_us-gaap_FairValueInputsLevel1Member_019c76d5-3dc0-7e15-94a2-2f09d0707684" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel2Member_019c76d5-3dc0-7537-98ac-1c00a91edf32" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueInputsLevel2Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueInputsLevel12And3Member_019c76d5-3dc0-7ed2-ace9-2efbe6df4000" xlink:to="loc_us-gaap_FairValueInputsLevel2Member_019c76d5-3dc0-7537-98ac-1c00a91edf32" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel3Member_019c76d5-3dc0-7eb3-9d06-4d9aa199f2aa" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueInputsLevel3Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueInputsLevel12And3Member_019c76d5-3dc0-7ed2-ace9-2efbe6df4000" xlink:to="loc_us-gaap_FairValueInputsLevel3Member_019c76d5-3dc0-7eb3-9d06-4d9aa199f2aa" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentAxis_019c76d5-3dc0-7723-be40-0c9d90d7ea37" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancialInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_019c76d5-3dc0-7ad1-887d-3a9b763660bc" xlink:to="loc_us-gaap_FinancialInstrumentAxis_019c76d5-3dc0-7723-be40-0c9d90d7ea37" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019c76d5-3dc0-7723-be40-0c9d90d7ea37_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_019c76d5-3dc0-7723-be40-0c9d90d7ea37" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019c76d5-3dc0-7723-be40-0c9d90d7ea37_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019c76d5-3dc0-7129-b68a-10c34d97a0e2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_019c76d5-3dc0-7723-be40-0c9d90d7ea37" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019c76d5-3dc0-7129-b68a-10c34d97a0e2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_USTreasuryAndGovernmentMember_019c76d5-3dc0-7916-af64-493e595fb8e2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_USTreasuryAndGovernmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019c76d5-3dc0-7129-b68a-10c34d97a0e2" xlink:to="loc_us-gaap_USTreasuryAndGovernmentMember_019c76d5-3dc0-7916-af64-493e595fb8e2" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommercialMortgageBackedSecuritiesMember_019c76d5-3dc0-7ed8-8b65-5b3186c7890f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommercialMortgageBackedSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019c76d5-3dc0-7129-b68a-10c34d97a0e2" xlink:to="loc_us-gaap_CommercialMortgageBackedSecuritiesMember_019c76d5-3dc0-7ed8-8b65-5b3186c7890f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ResidentialMortgageBackedSecuritiesMember_019c76d5-3dc0-76de-b5b1-6c351ae12b0c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ResidentialMortgageBackedSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019c76d5-3dc0-7129-b68a-10c34d97a0e2" xlink:to="loc_us-gaap_ResidentialMortgageBackedSecuritiesMember_019c76d5-3dc0-76de-b5b1-6c351ae12b0c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherDebtSecuritiesMember_019c76d5-3dc0-7602-9d39-b3cd917f7a5c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherDebtSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019c76d5-3dc0-7129-b68a-10c34d97a0e2" xlink:to="loc_us-gaap_OtherDebtSecuritiesMember_019c76d5-3dc0-7602-9d39-b3cd917f7a5c" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ResidentialMortgageMember_019dc038-f214-7861-abc3-b991946643c6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ResidentialMortgageMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019c76d5-3dc0-7129-b68a-10c34d97a0e2" xlink:to="loc_us-gaap_ResidentialMortgageMember_019dc038-f214-7861-abc3-b991946643c6" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TradingSecurities_019c76d5-3dc0-79c9-8a4e-30b191901ba4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TradingSecurities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019c76d5-3dc0-711e-b7db-f692a5add711" xlink:to="loc_us-gaap_TradingSecurities_019c76d5-3dc0-79c9-8a4e-30b191901ba4" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleExcludingAccruedInterest_019c76d5-3dc0-7755-b727-390d1244d37f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtSecuritiesAvailableForSaleExcludingAccruedInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019c76d5-3dc0-711e-b7db-f692a5add711" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleExcludingAccruedInterest_019c76d5-3dc0-7755-b727-390d1244d37f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquitySecuritiesFvNi_019c76d5-3dc0-755a-a48e-a2f326683c00" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EquitySecuritiesFvNi"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019c76d5-3dc0-711e-b7db-f692a5add711" xlink:to="loc_us-gaap_EquitySecuritiesFvNi_019c76d5-3dc0-755a-a48e-a2f326683c00" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LoansHeldForSaleFairValueDisclosure_019c76d5-3dc0-7305-80d7-fce7ec6cf5d7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LoansHeldForSaleFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019c76d5-3dc0-711e-b7db-f692a5add711" xlink:to="loc_us-gaap_LoansHeldForSaleFairValueDisclosure_019c76d5-3dc0-7305-80d7-fce7ec6cf5d7" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ServicingAssetAtFairValueAmount_019dc038-50fa-7b85-b044-21d21f30679d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ServicingAssetAtFairValueAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019c76d5-3dc0-711e-b7db-f692a5add711" xlink:to="loc_us-gaap_ServicingAssetAtFairValueAmount_019dc038-50fa-7b85-b044-21d21f30679d" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherAssetsFairValueDisclosure_019c76d5-3dc0-7ae2-bb8b-de82973b0a9b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherAssetsFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019c76d5-3dc0-711e-b7db-f692a5add711" xlink:to="loc_us-gaap_OtherAssetsFairValueDisclosure_019c76d5-3dc0-7ae2-bb8b-de82973b0a9b" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsFairValueDisclosure_019c76d5-3dc0-7f47-a4f5-55b27a8aa629" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AssetsFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019c76d5-3dc0-711e-b7db-f692a5add711" xlink:to="loc_us-gaap_AssetsFairValueDisclosure_019c76d5-3dc0-7f47-a4f5-55b27a8aa629" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherLiabilitiesFairValueDisclosure_019c76d5-3dc0-78ac-a986-624e17c33d16" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherLiabilitiesFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019c76d5-3dc0-711e-b7db-f692a5add711" xlink:to="loc_us-gaap_OtherLiabilitiesFairValueDisclosure_019c76d5-3dc0-78ac-a986-624e17c33d16" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesFairValueDisclosure_019c76d5-3dc0-799c-80d8-831f41a3e0dc" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LiabilitiesFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019c76d5-3dc0-711e-b7db-f692a5add711" xlink:to="loc_us-gaap_LiabilitiesFairValueDisclosure_019c76d5-3dc0-799c-80d8-831f41a3e0dc" xlink:type="arc" order="8"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.mtb.com/role/FairvaluemeasurementsAdditionalInformationDetail" xlink:type="simple" xlink:href="mtb-20260331.xsd#FairvaluemeasurementsAdditionalInformationDetail"/>
  <link:definitionLink xlink:role="http://www.mtb.com/role/FairvaluemeasurementsAdditionalInformationDetail" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019c76d5-3dc0-74bf-8868-79dfd904ac0f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_019c76d5-3dc0-745b-bf10-db2006e9d3e4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019c76d5-3dc0-74bf-8868-79dfd904ac0f" xlink:to="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_019c76d5-3dc0-745b-bf10-db2006e9d3e4" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019c76d5-3dc0-7568-a0ee-28f84876c651" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_019c76d5-3dc0-745b-bf10-db2006e9d3e4" xlink:to="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019c76d5-3dc0-7568-a0ee-28f84876c651" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019c76d5-3dc0-7568-a0ee-28f84876c651_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019c76d5-3dc0-7568-a0ee-28f84876c651" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019c76d5-3dc0-7568-a0ee-28f84876c651_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019c76d5-3dc0-7302-848c-44dee651d186" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019c76d5-3dc0-7568-a0ee-28f84876c651" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019c76d5-3dc0-7302-848c-44dee651d186" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel2Member_019c76d5-3dc0-7a33-87dc-175cc53f4b4f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueInputsLevel2Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019c76d5-3dc0-7302-848c-44dee651d186" xlink:to="loc_us-gaap_FairValueInputsLevel2Member_019c76d5-3dc0-7a33-87dc-175cc53f4b4f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel3Member_019c76d5-3dc0-774d-8451-2113b76fdb42" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueInputsLevel3Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019c76d5-3dc0-7302-848c-44dee651d186" xlink:to="loc_us-gaap_FairValueInputsLevel3Member_019c76d5-3dc0-774d-8451-2113b76fdb42" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentAxis_019c76d5-3dc0-71f4-a01b-72029c7ac6b9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancialInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_019c76d5-3dc0-745b-bf10-db2006e9d3e4" xlink:to="loc_us-gaap_FinancialInstrumentAxis_019c76d5-3dc0-71f4-a01b-72029c7ac6b9" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019c76d5-3dc0-71f4-a01b-72029c7ac6b9_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_019c76d5-3dc0-71f4-a01b-72029c7ac6b9" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019c76d5-3dc0-71f4-a01b-72029c7ac6b9_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019c76d5-3dc0-7b80-8d4f-1893e67a94b9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_019c76d5-3dc0-71f4-a01b-72029c7ac6b9" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019c76d5-3dc0-7b80-8d4f-1893e67a94b9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ResidentialMortgageMember_019c76d5-3dc0-78bb-aa86-cf4d1c2bf908" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ResidentialMortgageMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019c76d5-3dc0-7b80-8d4f-1893e67a94b9" xlink:to="loc_us-gaap_ResidentialMortgageMember_019c76d5-3dc0-78bb-aa86-cf4d1c2bf908" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LoansReceivableFairValueDisclosure_019c76d5-3dc0-7e62-a00c-08785580fa91" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LoansReceivableFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019c76d5-3dc0-74bf-8868-79dfd904ac0f" xlink:to="loc_us-gaap_LoansReceivableFairValueDisclosure_019c76d5-3dc0-7e62-a00c-08785580fa91" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_IncreaseDecreaseInFairValueOfNonrecurringFairValueMeasuredLoansForChargeOffsAndImpairmentReserves_019c76d5-3dc0-7413-9997-5b810c36be15" xlink:href="mtb-20260331.xsd#mtb_IncreaseDecreaseInFairValueOfNonrecurringFairValueMeasuredLoansForChargeOffsAndImpairmentReserves"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019c76d5-3dc0-74bf-8868-79dfd904ac0f" xlink:to="loc_mtb_IncreaseDecreaseInFairValueOfNonrecurringFairValueMeasuredLoansForChargeOffsAndImpairmentReserves_019c76d5-3dc0-7413-9997-5b810c36be15" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ServicingAssetAtAmortizedValueValuationAllowance_019c76d5-3dc0-7a89-8522-f03bd6bd62b7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ServicingAssetAtAmortizedValueValuationAllowance"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019c76d5-3dc0-74bf-8868-79dfd904ac0f" xlink:to="loc_us-gaap_ServicingAssetAtAmortizedValueValuationAllowance_019c76d5-3dc0-7a89-8522-f03bd6bd62b7" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.mtb.com/role/FairvaluemeasurementsMortgageServicingRightsFairValueMeasurementInputsDetail" xlink:type="simple" xlink:href="mtb-20260331.xsd#FairvaluemeasurementsMortgageServicingRightsFairValueMeasurementInputsDetail"/>
  <link:definitionLink xlink:role="http://www.mtb.com/role/FairvaluemeasurementsMortgageServicingRightsFairValueMeasurementInputsDetail" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems_019de522-6748-7887-a3b4-0bf8cdbdec50" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable_019de522-6748-733c-baf1-4ef7dfbae4f9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems_019de522-6748-7887-a3b4-0bf8cdbdec50" xlink:to="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable_019de522-6748-733c-baf1-4ef7dfbae4f9" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_019de522-6748-75ed-8c0b-e9eb77318b62" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable_019de522-6748-733c-baf1-4ef7dfbae4f9" xlink:to="loc_srt_RangeAxis_019de522-6748-75ed-8c0b-e9eb77318b62" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_019de522-6748-75ed-8c0b-e9eb77318b62_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_019de522-6748-75ed-8c0b-e9eb77318b62" xlink:to="loc_srt_RangeMember_019de522-6748-75ed-8c0b-e9eb77318b62_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_019de522-6748-733a-b747-5ad191c0544f" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_019de522-6748-75ed-8c0b-e9eb77318b62" xlink:to="loc_srt_RangeMember_019de522-6748-733a-b747-5ad191c0544f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_019de522-6748-7df1-8e21-2b7987c7b129" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_019de522-6748-733a-b747-5ad191c0544f" xlink:to="loc_srt_MinimumMember_019de522-6748-7df1-8e21-2b7987c7b129" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_019de522-6748-70f9-9d47-057e314d6b57" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_019de522-6748-733a-b747-5ad191c0544f" xlink:to="loc_srt_MaximumMember_019de522-6748-70f9-9d47-057e314d6b57" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MeasurementInputTypeAxis_019de522-6748-71b6-9fb0-d9d514561dea" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_MeasurementInputTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable_019de522-6748-733c-baf1-4ef7dfbae4f9" xlink:to="loc_us-gaap_MeasurementInputTypeAxis_019de522-6748-71b6-9fb0-d9d514561dea" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MeasurementInputTypeDomain_019de522-6748-71b6-9fb0-d9d514561dea_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_MeasurementInputTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_MeasurementInputTypeAxis_019de522-6748-71b6-9fb0-d9d514561dea" xlink:to="loc_us-gaap_MeasurementInputTypeDomain_019de522-6748-71b6-9fb0-d9d514561dea_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MeasurementInputTypeDomain_019de522-6748-7202-9233-cf58fc399dff" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_MeasurementInputTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_MeasurementInputTypeAxis_019de522-6748-71b6-9fb0-d9d514561dea" xlink:to="loc_us-gaap_MeasurementInputTypeDomain_019de522-6748-7202-9233-cf58fc399dff" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MeasurementInputPrepaymentRateMember_019de522-6748-7f19-96b5-82125085d2b1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_MeasurementInputPrepaymentRateMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MeasurementInputTypeDomain_019de522-6748-7202-9233-cf58fc399dff" xlink:to="loc_us-gaap_MeasurementInputPrepaymentRateMember_019de522-6748-7f19-96b5-82125085d2b1" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MeasurementInputCreditSpreadMember_019de522-6748-7bd3-8726-92a5e8799fe5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_MeasurementInputCreditSpreadMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MeasurementInputTypeDomain_019de522-6748-7202-9233-cf58fc399dff" xlink:to="loc_us-gaap_MeasurementInputCreditSpreadMember_019de522-6748-7bd3-8726-92a5e8799fe5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ServicingAssetMeasurementInput_019de522-6748-7ca2-ad8c-4543971f8f58" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ServicingAssetMeasurementInput"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems_019de522-6748-7887-a3b4-0bf8cdbdec50" xlink:to="loc_us-gaap_ServicingAssetMeasurementInput_019de522-6748-7ca2-ad8c-4543971f8f58" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SensitivityAnalysisOfFairValueOfInterestsContinuedToBeHeldByTransferorServicingAssetsOrLiabilitiesImpactOf10PercentAdverseChangeInPrepaymentSpeed_019de522-6748-73bb-9170-520c6aa0c859" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SensitivityAnalysisOfFairValueOfInterestsContinuedToBeHeldByTransferorServicingAssetsOrLiabilitiesImpactOf10PercentAdverseChangeInPrepaymentSpeed"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems_019de522-6748-7887-a3b4-0bf8cdbdec50" xlink:to="loc_us-gaap_SensitivityAnalysisOfFairValueOfInterestsContinuedToBeHeldByTransferorServicingAssetsOrLiabilitiesImpactOf10PercentAdverseChangeInPrepaymentSpeed_019de522-6748-73bb-9170-520c6aa0c859" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SensitivityAnalysisOfFairValueOfInterestsContinuedToBeHeldByTransferorServicingAssetsOrLiabilitiesImpactOf20PercentAdverseChangeInPrepaymentSpeed_019de522-6748-7345-b127-180f7d8379d3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SensitivityAnalysisOfFairValueOfInterestsContinuedToBeHeldByTransferorServicingAssetsOrLiabilitiesImpactOf20PercentAdverseChangeInPrepaymentSpeed"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems_019de522-6748-7887-a3b4-0bf8cdbdec50" xlink:to="loc_us-gaap_SensitivityAnalysisOfFairValueOfInterestsContinuedToBeHeldByTransferorServicingAssetsOrLiabilitiesImpactOf20PercentAdverseChangeInPrepaymentSpeed_019de522-6748-7345-b127-180f7d8379d3" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SensitivityAnalysisOfFairValueOfInterestsContinuedToBeHeldByTransferorServicingAssetsOrLiabilitiesImpactOf10PercentAdverseChangeInOtherAssumption_019de522-6748-7ee9-863a-215947edc960" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SensitivityAnalysisOfFairValueOfInterestsContinuedToBeHeldByTransferorServicingAssetsOrLiabilitiesImpactOf10PercentAdverseChangeInOtherAssumption"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems_019de522-6748-7887-a3b4-0bf8cdbdec50" xlink:to="loc_us-gaap_SensitivityAnalysisOfFairValueOfInterestsContinuedToBeHeldByTransferorServicingAssetsOrLiabilitiesImpactOf10PercentAdverseChangeInOtherAssumption_019de522-6748-7ee9-863a-215947edc960" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SensitivityAnalysisOfFairValueOfInterestsContinuedToBeHeldByTransferorServicingAssetsOrLiabilitiesImpactOf20PercentAdverseChangeInOtherAssumption_019de522-6748-7847-99e4-4b90fd056fb8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SensitivityAnalysisOfFairValueOfInterestsContinuedToBeHeldByTransferorServicingAssetsOrLiabilitiesImpactOf20PercentAdverseChangeInOtherAssumption"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems_019de522-6748-7887-a3b4-0bf8cdbdec50" xlink:to="loc_us-gaap_SensitivityAnalysisOfFairValueOfInterestsContinuedToBeHeldByTransferorServicingAssetsOrLiabilitiesImpactOf20PercentAdverseChangeInOtherAssumption_019de522-6748-7847-99e4-4b90fd056fb8" xlink:type="arc" order="4"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.mtb.com/role/FairValueMeasurementsAssetsandLiabilitiesMeasuredatEstimatedFairValueonNonrecurringBasisDetail" xlink:type="simple" xlink:href="mtb-20260331.xsd#FairValueMeasurementsAssetsandLiabilitiesMeasuredatEstimatedFairValueonNonrecurringBasisDetail"/>
  <link:definitionLink xlink:role="http://www.mtb.com/role/FairValueMeasurementsAssetsandLiabilitiesMeasuredatEstimatedFairValueonNonrecurringBasisDetail" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019d49c3-62ae-722d-9dbf-804bf10c9712" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_019d49c3-62ae-7189-a1a1-47cc97cbb1e6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019d49c3-62ae-722d-9dbf-804bf10c9712" xlink:to="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_019d49c3-62ae-7189-a1a1-47cc97cbb1e6" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019d49c3-62ae-7d0d-ad88-3004abe97e4d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_019d49c3-62ae-7189-a1a1-47cc97cbb1e6" xlink:to="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019d49c3-62ae-7d0d-ad88-3004abe97e4d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019d49c3-62ae-7d0d-ad88-3004abe97e4d_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019d49c3-62ae-7d0d-ad88-3004abe97e4d" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019d49c3-62ae-7d0d-ad88-3004abe97e4d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019d49c3-62ae-777e-8af1-278bbd7fc95e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019d49c3-62ae-7d0d-ad88-3004abe97e4d" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019d49c3-62ae-777e-8af1-278bbd7fc95e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel1Member_019d49c3-62ae-7470-9561-e2e05361fe21" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueInputsLevel1Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019d49c3-62ae-777e-8af1-278bbd7fc95e" xlink:to="loc_us-gaap_FairValueInputsLevel1Member_019d49c3-62ae-7470-9561-e2e05361fe21" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel2Member_019d49c3-62ae-7072-b7c5-e9aa5806086e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueInputsLevel2Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019d49c3-62ae-777e-8af1-278bbd7fc95e" xlink:to="loc_us-gaap_FairValueInputsLevel2Member_019d49c3-62ae-7072-b7c5-e9aa5806086e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel3Member_019d49c3-62ae-7a82-ad26-0af736f5fa0d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueInputsLevel3Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019d49c3-62ae-777e-8af1-278bbd7fc95e" xlink:to="loc_us-gaap_FairValueInputsLevel3Member_019d49c3-62ae-7a82-ad26-0af736f5fa0d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LoansReceivableFairValueDisclosure_019d49c3-62ae-789e-9a06-162d81e7f0fe" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LoansReceivableFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019d49c3-62ae-722d-9dbf-804bf10c9712" xlink:to="loc_us-gaap_LoansReceivableFairValueDisclosure_019d49c3-62ae-789e-9a06-162d81e7f0fe" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_IncreaseDecreaseInFairValueOfNonrecurringFairValueMeasuredLoansForChargeOffsAndImpairmentReserves_019d49c3-62ae-7f3f-8137-0e638771359b" xlink:href="mtb-20260331.xsd#mtb_IncreaseDecreaseInFairValueOfNonrecurringFairValueMeasuredLoansForChargeOffsAndImpairmentReserves"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019d49c3-62ae-722d-9dbf-804bf10c9712" xlink:to="loc_mtb_IncreaseDecreaseInFairValueOfNonrecurringFairValueMeasuredLoansForChargeOffsAndImpairmentReserves_019d49c3-62ae-7f3f-8137-0e638771359b" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.mtb.com/role/FairvaluemeasurementsCarryingAmountsandEstimatedFairValueforFinancialInstrumentAssetsLiabilitiesDetail" xlink:type="simple" xlink:href="mtb-20260331.xsd#FairvaluemeasurementsCarryingAmountsandEstimatedFairValueforFinancialInstrumentAssetsLiabilitiesDetail"/>
  <link:definitionLink xlink:role="http://www.mtb.com/role/FairvaluemeasurementsCarryingAmountsandEstimatedFairValueforFinancialInstrumentAssetsLiabilitiesDetail" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_019c76d5-3dc0-75b8-8df4-2492c967ae3f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByBalanceSheetGroupingTable_019c76d5-3dc0-7391-b418-e25cac29e76d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueByBalanceSheetGroupingTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_019c76d5-3dc0-75b8-8df4-2492c967ae3f" xlink:to="loc_us-gaap_FairValueByBalanceSheetGroupingTable_019c76d5-3dc0-7391-b418-e25cac29e76d" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByMeasurementBasisAxis_019c76d5-3dc0-77a2-8c7b-a162961f055d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueByMeasurementBasisAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueByBalanceSheetGroupingTable_019c76d5-3dc0-7391-b418-e25cac29e76d" xlink:to="loc_us-gaap_FairValueByMeasurementBasisAxis_019c76d5-3dc0-77a2-8c7b-a162961f055d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_019c76d5-3dc0-77a2-8c7b-a162961f055d_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PortionAtFairValueFairValueDisclosureMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByMeasurementBasisAxis_019c76d5-3dc0-77a2-8c7b-a162961f055d" xlink:to="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_019c76d5-3dc0-77a2-8c7b-a162961f055d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueDisclosureItemAmountsDomain_019c76d5-3dc0-7188-8f79-bbddbb00cf45" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueDisclosureItemAmountsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByMeasurementBasisAxis_019c76d5-3dc0-77a2-8c7b-a162961f055d" xlink:to="loc_us-gaap_FairValueDisclosureItemAmountsDomain_019c76d5-3dc0-7188-8f79-bbddbb00cf45" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_019c76d5-3dc0-7414-9164-77b58b288cb0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PortionAtFairValueFairValueDisclosureMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueDisclosureItemAmountsDomain_019c76d5-3dc0-7188-8f79-bbddbb00cf45" xlink:to="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_019c76d5-3dc0-7414-9164-77b58b288cb0" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CarryingReportedAmountFairValueDisclosureMember_019c76d5-3dc0-7386-b03b-8a368e7de8e8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CarryingReportedAmountFairValueDisclosureMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_019c76d5-3dc0-7414-9164-77b58b288cb0" xlink:to="loc_us-gaap_CarryingReportedAmountFairValueDisclosureMember_019c76d5-3dc0-7386-b03b-8a368e7de8e8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EstimateOfFairValueFairValueDisclosureMember_019c76d5-3dc0-7963-8740-d8942454ea86" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EstimateOfFairValueFairValueDisclosureMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_019c76d5-3dc0-7414-9164-77b58b288cb0" xlink:to="loc_us-gaap_EstimateOfFairValueFairValueDisclosureMember_019c76d5-3dc0-7963-8740-d8942454ea86" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019c76d5-3dc0-7c02-931b-b7f0d6202edb" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueByBalanceSheetGroupingTable_019c76d5-3dc0-7391-b418-e25cac29e76d" xlink:to="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019c76d5-3dc0-7c02-931b-b7f0d6202edb" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019c76d5-3dc0-7c02-931b-b7f0d6202edb_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019c76d5-3dc0-7c02-931b-b7f0d6202edb" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019c76d5-3dc0-7c02-931b-b7f0d6202edb_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019c76d5-3dc0-7af1-b44d-a707ba46e84f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019c76d5-3dc0-7c02-931b-b7f0d6202edb" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019c76d5-3dc0-7af1-b44d-a707ba46e84f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel1Member_019c76d5-3dc0-7fa1-b443-c5749d3db6f9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueInputsLevel1Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019c76d5-3dc0-7af1-b44d-a707ba46e84f" xlink:to="loc_us-gaap_FairValueInputsLevel1Member_019c76d5-3dc0-7fa1-b443-c5749d3db6f9" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel2Member_019c76d5-3dc0-7527-813b-b494f95c86e6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueInputsLevel2Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019c76d5-3dc0-7af1-b44d-a707ba46e84f" xlink:to="loc_us-gaap_FairValueInputsLevel2Member_019c76d5-3dc0-7527-813b-b494f95c86e6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel3Member_019c76d5-3dc0-786e-96d3-4ccd2bad9a7a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueInputsLevel3Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019c76d5-3dc0-7af1-b44d-a707ba46e84f" xlink:to="loc_us-gaap_FairValueInputsLevel3Member_019c76d5-3dc0-786e-96d3-4ccd2bad9a7a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentsFinancialAssetsBalanceSheetGroupingsAbstract_019c76d5-3dc0-7c23-95d8-123fd21dace9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancialInstrumentsFinancialAssetsBalanceSheetGroupingsAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_019c76d5-3dc0-75b8-8df4-2492c967ae3f" xlink:to="loc_us-gaap_FinancialInstrumentsFinancialAssetsBalanceSheetGroupingsAbstract_019c76d5-3dc0-7c23-95d8-123fd21dace9" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_019c76d5-3dc0-7421-9c3a-7c2e3347ac84" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CashAndCashEquivalentsAtCarryingValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancialInstrumentsFinancialAssetsBalanceSheetGroupingsAbstract_019c76d5-3dc0-7c23-95d8-123fd21dace9" xlink:to="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_019c76d5-3dc0-7421-9c3a-7c2e3347ac84" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestBearingDepositsInBanks_019c76d5-3dc0-79ca-8db5-ea1e2e3c5c98" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InterestBearingDepositsInBanks"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancialInstrumentsFinancialAssetsBalanceSheetGroupingsAbstract_019c76d5-3dc0-7c23-95d8-123fd21dace9" xlink:to="loc_us-gaap_InterestBearingDepositsInBanks_019c76d5-3dc0-79ca-8db5-ea1e2e3c5c98" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Investments_019c76d5-3dc0-7f4d-bbb5-cc63388b7d01" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_Investments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancialInstrumentsFinancialAssetsBalanceSheetGroupingsAbstract_019c76d5-3dc0-7c23-95d8-123fd21dace9" xlink:to="loc_us-gaap_Investments_019c76d5-3dc0-7f4d-bbb5-cc63388b7d01" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestAfterAllowanceForCreditLoss_019c76d5-3dc0-726f-82fa-a2970ac2161e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestAfterAllowanceForCreditLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancialInstrumentsFinancialAssetsBalanceSheetGroupingsAbstract_019c76d5-3dc0-7c23-95d8-123fd21dace9" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterestAfterAllowanceForCreditLoss_019c76d5-3dc0-726f-82fa-a2970ac2161e" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentsFinancialLiabilitiesBalanceSheetGroupingsAbstract_019c76d5-3dc0-7b1e-94f5-79f62578d853" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancialInstrumentsFinancialLiabilitiesBalanceSheetGroupingsAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_019c76d5-3dc0-75b8-8df4-2492c967ae3f" xlink:to="loc_us-gaap_FinancialInstrumentsFinancialLiabilitiesBalanceSheetGroupingsAbstract_019c76d5-3dc0-7b1e-94f5-79f62578d853" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_TimeDepositsFairValueDisclosure_019c76d5-3dc0-76b6-ac29-a053eb8de7aa" xlink:href="mtb-20260331.xsd#mtb_TimeDepositsFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancialInstrumentsFinancialLiabilitiesBalanceSheetGroupingsAbstract_019c76d5-3dc0-7b1e-94f5-79f62578d853" xlink:to="loc_mtb_TimeDepositsFairValueDisclosure_019c76d5-3dc0-76b6-ac29-a053eb8de7aa" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FederalFundsPurchasedAndSecuritiesSoldUnderAgreementsToRepurchase_019c76d5-3dc0-77df-8a0f-f617b578320e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FederalFundsPurchasedAndSecuritiesSoldUnderAgreementsToRepurchase"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancialInstrumentsFinancialLiabilitiesBalanceSheetGroupingsAbstract_019c76d5-3dc0-7b1e-94f5-79f62578d853" xlink:to="loc_us-gaap_FederalFundsPurchasedAndSecuritiesSoldUnderAgreementsToRepurchase_019c76d5-3dc0-77df-8a0f-f617b578320e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebt_019c76d5-3dc0-737e-b06a-753d48c188e8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongTermDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancialInstrumentsFinancialLiabilitiesBalanceSheetGroupingsAbstract_019c76d5-3dc0-7b1e-94f5-79f62578d853" xlink:to="loc_us-gaap_LongTermDebt_019c76d5-3dc0-737e-b06a-753d48c188e8" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TimeDepositLiabilityAboveUsInsuranceLimit_019d4e6e-7daa-7e21-ab72-2d067e2a2d21" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TimeDepositLiabilityAboveUsInsuranceLimit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_019c76d5-3dc0-75b8-8df4-2492c967ae3f" xlink:to="loc_us-gaap_TimeDepositLiabilityAboveUsInsuranceLimit_019d4e6e-7daa-7e21-ab72-2d067e2a2d21" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.mtb.com/role/CommitmentsandcontingenciesAdditionalInformationDetail" xlink:type="simple" xlink:href="mtb-20260331.xsd#CommitmentsandcontingenciesAdditionalInformationDetail"/>
  <link:definitionLink xlink:role="http://www.mtb.com/role/CommitmentsandcontingenciesAdditionalInformationDetail" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LossContingenciesLineItems_019c76d5-3dc0-7b27-9c55-9b880092eb3d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LossContingenciesLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LossContingenciesTable_019c76d5-3dc0-7ae8-b3ff-174c50b201f9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LossContingenciesTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_LossContingenciesLineItems_019c76d5-3dc0-7b27-9c55-9b880092eb3d" xlink:to="loc_us-gaap_LossContingenciesTable_019c76d5-3dc0-7ae8-b3ff-174c50b201f9" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_019c76d5-3dc0-7b40-a465-eb445452a071" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LossContingenciesTable_019c76d5-3dc0-7ae8-b3ff-174c50b201f9" xlink:to="loc_srt_RangeAxis_019c76d5-3dc0-7b40-a465-eb445452a071" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_019c76d5-3dc0-7b40-a465-eb445452a071_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_019c76d5-3dc0-7b40-a465-eb445452a071" xlink:to="loc_srt_RangeMember_019c76d5-3dc0-7b40-a465-eb445452a071_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_019c76d5-3dc0-7632-8207-4a19572e6ff3" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_019c76d5-3dc0-7b40-a465-eb445452a071" xlink:to="loc_srt_RangeMember_019c76d5-3dc0-7632-8207-4a19572e6ff3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_019c76d5-3dc0-70d5-9839-39e38f075f23" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_019c76d5-3dc0-7632-8207-4a19572e6ff3" xlink:to="loc_srt_MinimumMember_019c76d5-3dc0-70d5-9839-39e38f075f23" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_019c76d5-3dc0-7359-9a50-2f38218728af" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_019c76d5-3dc0-7632-8207-4a19572e6ff3" xlink:to="loc_srt_MaximumMember_019c76d5-3dc0-7359-9a50-2f38218728af" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LegalEntityAxis_019db08d-da59-75b5-b65e-5459e4666a39" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_LegalEntityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LossContingenciesTable_019c76d5-3dc0-7ae8-b3ff-174c50b201f9" xlink:to="loc_dei_LegalEntityAxis_019db08d-da59-75b5-b65e-5459e4666a39" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019db08d-da59-75b5-b65e-5459e4666a39_default" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_019db08d-da59-75b5-b65e-5459e4666a39" xlink:to="loc_dei_EntityDomain_019db08d-da59-75b5-b65e-5459e4666a39_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019db08d-da59-7a73-ab2e-b16c463f3247" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_019db08d-da59-75b5-b65e-5459e4666a39" xlink:to="loc_dei_EntityDomain_019db08d-da59-7a73-ab2e-b16c463f3247" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_TricolorHoldingsLLCMember_019db08d-da59-7274-9b5d-112e10b7a09e" xlink:href="mtb-20260331.xsd#mtb_TricolorHoldingsLLCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_019db08d-da59-7a73-ab2e-b16c463f3247" xlink:to="loc_mtb_TricolorHoldingsLLCMember_019db08d-da59-7274-9b5d-112e10b7a09e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_CommitmentsToExtendCreditToCommercialCustomers_019c76d5-3dc0-7e9d-b3ac-b751d6d2e28f" xlink:href="mtb-20260331.xsd#mtb_CommitmentsToExtendCreditToCommercialCustomers"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_019c76d5-3dc0-7b27-9c55-9b880092eb3d" xlink:to="loc_mtb_CommitmentsToExtendCreditToCommercialCustomers_019c76d5-3dc0-7e9d-b3ac-b751d6d2e28f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_MaximumCreditRiskForRecourseAssociatedWithLoansSoldUnderFederalNationalMortgageAssociationDelegatedUnderwritingAndServicingProgram_019c76d5-3dc0-7eb0-afa6-b4dec8cb81e9" xlink:href="mtb-20260331.xsd#mtb_MaximumCreditRiskForRecourseAssociatedWithLoansSoldUnderFederalNationalMortgageAssociationDelegatedUnderwritingAndServicingProgram"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_019c76d5-3dc0-7b27-9c55-9b880092eb3d" xlink:to="loc_mtb_MaximumCreditRiskForRecourseAssociatedWithLoansSoldUnderFederalNationalMortgageAssociationDelegatedUnderwritingAndServicingProgram_019c76d5-3dc0-7eb0-afa6-b4dec8cb81e9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LossContingencyAccrualAtCarryingValue_019c76d5-3dc0-74e3-8c8c-4baca23cc191" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LossContingencyAccrualAtCarryingValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_019c76d5-3dc0-7b27-9c55-9b880092eb3d" xlink:to="loc_us-gaap_LossContingencyAccrualAtCarryingValue_019c76d5-3dc0-74e3-8c8c-4baca23cc191" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LossContingencyEstimateOfPossibleLoss_019c76d5-3dc0-7ea2-af0f-06a1e8525411" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LossContingencyEstimateOfPossibleLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_019c76d5-3dc0-7b27-9c55-9b880092eb3d" xlink:to="loc_us-gaap_LossContingencyEstimateOfPossibleLoss_019c76d5-3dc0-7ea2-af0f-06a1e8525411" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_CommitmentsAndContingenciesFictitiousLoans_019db08d-da59-721a-9811-aab8ae031967" xlink:href="mtb-20260331.xsd#mtb_CommitmentsAndContingenciesFictitiousLoans"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_019c76d5-3dc0-7b27-9c55-9b880092eb3d" xlink:to="loc_mtb_CommitmentsAndContingenciesFictitiousLoans_019db08d-da59-721a-9811-aab8ae031967" xlink:type="arc" order="4"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.mtb.com/role/SegmentinformationInformationaboutCompanysSegmentsDetail" xlink:type="simple" xlink:href="mtb-20260331.xsd#SegmentinformationInformationaboutCompanysSegmentsDetail"/>
  <link:definitionLink xlink:role="http://www.mtb.com/role/SegmentinformationInformationaboutCompanysSegmentsDetail" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentReportingInformationLineItems_019c76d5-3dc0-75c0-816c-2146203839dd" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SegmentReportingInformationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019c76d5-3dc0-7504-b2f4-f48eb76f98bd" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019c76d5-3dc0-75c0-816c-2146203839dd" xlink:to="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019c76d5-3dc0-7504-b2f4-f48eb76f98bd" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_019c76d5-3dc0-7550-af43-acd48fc4b454" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019c76d5-3dc0-7504-b2f4-f48eb76f98bd" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_019c76d5-3dc0-7550-af43-acd48fc4b454" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_019c76d5-3dc0-7550-af43-acd48fc4b454_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_019c76d5-3dc0-7550-af43-acd48fc4b454" xlink:to="loc_us-gaap_SegmentDomain_019c76d5-3dc0-7550-af43-acd48fc4b454_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_019c76d5-3dc0-78ea-a250-82f3a106c98d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_019c76d5-3dc0-7550-af43-acd48fc4b454" xlink:to="loc_us-gaap_SegmentDomain_019c76d5-3dc0-78ea-a250-82f3a106c98d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_CommercialBankingMember_019c76d5-3dc0-77a0-96cb-f6ae9bef3c21" xlink:href="mtb-20260331.xsd#mtb_CommercialBankingMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_019c76d5-3dc0-78ea-a250-82f3a106c98d" xlink:to="loc_mtb_CommercialBankingMember_019c76d5-3dc0-77a0-96cb-f6ae9bef3c21" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_RetailBankingMember_019c76d5-3dc0-7ae2-a746-92954f9b34c5" xlink:href="mtb-20260331.xsd#mtb_RetailBankingMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_019c76d5-3dc0-78ea-a250-82f3a106c98d" xlink:to="loc_mtb_RetailBankingMember_019c76d5-3dc0-7ae2-a746-92954f9b34c5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_InstitutionalServicesAndWealthManagementMember_019c76d5-3dc0-7b7d-b219-7ecfdf5c78fc" xlink:href="mtb-20260331.xsd#mtb_InstitutionalServicesAndWealthManagementMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_019c76d5-3dc0-78ea-a250-82f3a106c98d" xlink:to="loc_mtb_InstitutionalServicesAndWealthManagementMember_019c76d5-3dc0-7b7d-b219-7ecfdf5c78fc" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AllOtherSegmentsMember_019c76d5-3dc0-71fa-a2dd-7a90108311bc" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AllOtherSegmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_019c76d5-3dc0-78ea-a250-82f3a106c98d" xlink:to="loc_us-gaap_AllOtherSegmentsMember_019c76d5-3dc0-71fa-a2dd-7a90108311bc" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsAxis_019c76d5-3dc0-709b-98c5-b93c4ad5b0c0" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ConsolidationItemsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019c76d5-3dc0-7504-b2f4-f48eb76f98bd" xlink:to="loc_srt_ConsolidationItemsAxis_019c76d5-3dc0-709b-98c5-b93c4ad5b0c0" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_019c76d5-3dc0-709b-98c5-b93c4ad5b0c0_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidationItemsAxis_019c76d5-3dc0-709b-98c5-b93c4ad5b0c0" xlink:to="loc_srt_ConsolidationItemsDomain_019c76d5-3dc0-709b-98c5-b93c4ad5b0c0_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_019c76d5-3dc0-73ef-999d-32fce6851d36" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidationItemsAxis_019c76d5-3dc0-709b-98c5-b93c4ad5b0c0" xlink:to="loc_srt_ConsolidationItemsDomain_019c76d5-3dc0-73ef-999d-32fce6851d36" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingSegmentsMember_019c76d5-3dc0-7854-ba07-1501b607092b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OperatingSegmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_019c76d5-3dc0-73ef-999d-32fce6851d36" xlink:to="loc_us-gaap_OperatingSegmentsMember_019c76d5-3dc0-7854-ba07-1501b607092b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestIncomeExpenseNet_019c76d5-3dc0-7bea-92ae-4d47728e717a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InterestIncomeExpenseNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019c76d5-3dc0-75c0-816c-2146203839dd" xlink:to="loc_us-gaap_InterestIncomeExpenseNet_019c76d5-3dc0-7bea-92ae-4d47728e717a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NoninterestIncome_019c76d5-3dc0-7e88-be19-8b1c92dbe9af" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NoninterestIncome"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019c76d5-3dc0-75c0-816c-2146203839dd" xlink:to="loc_us-gaap_NoninterestIncome_019c76d5-3dc0-7e88-be19-8b1c92dbe9af" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Revenues_019c76d5-3dc0-7860-8844-ded0f20a477f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_Revenues"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019c76d5-3dc0-75c0-816c-2146203839dd" xlink:to="loc_us-gaap_Revenues_019c76d5-3dc0-7860-8844-ded0f20a477f" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_FinancingReceivableAndUnfundedCommitmentsExcludingAccruedInterestCreditLossExpenseReversal_019c76d5-3dc0-7b88-81a8-212de8e6ef47" xlink:href="mtb-20260331.xsd#mtb_FinancingReceivableAndUnfundedCommitmentsExcludingAccruedInterestCreditLossExpenseReversal"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019c76d5-3dc0-75c0-816c-2146203839dd" xlink:to="loc_mtb_FinancingReceivableAndUnfundedCommitmentsExcludingAccruedInterestCreditLossExpenseReversal_019c76d5-3dc0-7b88-81a8-212de8e6ef47" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestCreditLossExpenseReversal_019c76d5-3dc0-7544-b36f-1328b5fa32eb" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestCreditLossExpenseReversal"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019c76d5-3dc0-75c0-816c-2146203839dd" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterestCreditLossExpenseReversal_019c76d5-3dc0-7544-b36f-1328b5fa32eb" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LaborAndRelatedExpense_019c76d5-3dc0-719d-b30e-f9abb1459d03" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LaborAndRelatedExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019c76d5-3dc0-75c0-816c-2146203839dd" xlink:to="loc_us-gaap_LaborAndRelatedExpense_019c76d5-3dc0-719d-b30e-f9abb1459d03" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DepreciationDepletionAndAmortization_019c76d5-3dc0-7f42-bd0e-ef303c9905b3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DepreciationDepletionAndAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019c76d5-3dc0-75c0-816c-2146203839dd" xlink:to="loc_us-gaap_DepreciationDepletionAndAmortization_019c76d5-3dc0-7f42-bd0e-ef303c9905b3" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_OtherDirectExpenses_019c76d5-3dc0-7181-b6eb-26520a8caa43" xlink:href="mtb-20260331.xsd#mtb_OtherDirectExpenses"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019c76d5-3dc0-75c0-816c-2146203839dd" xlink:to="loc_mtb_OtherDirectExpenses_019c76d5-3dc0-7181-b6eb-26520a8caa43" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_IndirectExpenseIncome_019c76d5-3dc0-7d7d-89de-6ca35e5f8452" xlink:href="mtb-20260331.xsd#mtb_IndirectExpenseIncome"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019c76d5-3dc0-75c0-816c-2146203839dd" xlink:to="loc_mtb_IndirectExpenseIncome_019c76d5-3dc0-7d7d-89de-6ca35e5f8452" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_019c76d5-3dc0-76ef-9dd1-998b7d7c9939" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019c76d5-3dc0-75c0-816c-2146203839dd" xlink:to="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_019c76d5-3dc0-76ef-9dd1-998b7d7c9939" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxExpenseBenefit_019c76d5-3dc0-73b4-bb01-cd66276adcc9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeTaxExpenseBenefit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019c76d5-3dc0-75c0-816c-2146203839dd" xlink:to="loc_us-gaap_IncomeTaxExpenseBenefit_019c76d5-3dc0-73b4-bb01-cd66276adcc9" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_019c76d5-3dc0-7448-b5df-1a1a4dfb3526" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NetIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019c76d5-3dc0-75c0-816c-2146203839dd" xlink:to="loc_us-gaap_NetIncomeLoss_019c76d5-3dc0-7448-b5df-1a1a4dfb3526" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsAverageOutstanding_019c76d5-3dc0-7190-99ed-8971300eb883" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AssetsAverageOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019c76d5-3dc0-75c0-816c-2146203839dd" xlink:to="loc_us-gaap_AssetsAverageOutstanding_019c76d5-3dc0-7190-99ed-8971300eb883" xlink:type="arc" order="12"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.mtb.com/role/RelationshipwithBLGandBayviewFinancialDetail" xlink:type="simple" xlink:href="mtb-20260331.xsd#RelationshipwithBLGandBayviewFinancialDetail"/>
  <link:definitionLink xlink:role="http://www.mtb.com/role/RelationshipwithBLGandBayviewFinancialDetail" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019c76d5-3dc0-700a-9056-fc82a40a2a84" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfEquityMethodInvestmentsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_019c76d5-3dc0-76a2-be89-ea21563fcba3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfEquityMethodInvestmentsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019c76d5-3dc0-700a-9056-fc82a40a2a84" xlink:to="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_019c76d5-3dc0-76a2-be89-ea21563fcba3" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_019c76d5-3dc0-7c1b-b480-2f4ba27555de" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_019c76d5-3dc0-76a2-be89-ea21563fcba3" xlink:to="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_019c76d5-3dc0-7c1b-b480-2f4ba27555de" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_EquityMethodInvesteeNameDomain_019c76d5-3dc0-7c1b-b480-2f4ba27555de_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_EquityMethodInvesteeNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_019c76d5-3dc0-7c1b-b480-2f4ba27555de" xlink:to="loc_srt_EquityMethodInvesteeNameDomain_019c76d5-3dc0-7c1b-b480-2f4ba27555de_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_EquityMethodInvesteeNameDomain_019c76d5-3dc0-70fa-b812-f619e0b3fdc2" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_EquityMethodInvesteeNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_019c76d5-3dc0-7c1b-b480-2f4ba27555de" xlink:to="loc_srt_EquityMethodInvesteeNameDomain_019c76d5-3dc0-70fa-b812-f619e0b3fdc2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_BayviewLendingGroupMember_019c76d5-3dc0-769e-9463-f5c1c9975180" xlink:href="mtb-20260331.xsd#mtb_BayviewLendingGroupMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_019c76d5-3dc0-70fa-b812-f619e0b3fdc2" xlink:to="loc_mtb_BayviewLendingGroupMember_019c76d5-3dc0-769e-9463-f5c1c9975180" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_BayviewLendingGroupAndBayviewFinancialMember_019c76d5-3dc0-7e2e-a960-8b721fc4a9a7" xlink:href="mtb-20260331.xsd#mtb_BayviewLendingGroupAndBayviewFinancialMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_019c76d5-3dc0-70fa-b812-f619e0b3fdc2" xlink:to="loc_mtb_BayviewLendingGroupAndBayviewFinancialMember_019c76d5-3dc0-7e2e-a960-8b721fc4a9a7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_BayviewFinancialMember_019c76d5-3dc0-76a1-8471-21559a99b252" xlink:href="mtb-20260331.xsd#mtb_BayviewFinancialMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_019c76d5-3dc0-70fa-b812-f619e0b3fdc2" xlink:to="loc_mtb_BayviewFinancialMember_019c76d5-3dc0-76a1-8471-21559a99b252" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationAxis_019c76d5-3dc0-774a-885e-cb1258d269fa" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeStatementLocationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_019c76d5-3dc0-76a2-be89-ea21563fcba3" xlink:to="loc_us-gaap_IncomeStatementLocationAxis_019c76d5-3dc0-774a-885e-cb1258d269fa" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_019c76d5-3dc0-774a-885e-cb1258d269fa_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeStatementLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_019c76d5-3dc0-774a-885e-cb1258d269fa" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_019c76d5-3dc0-774a-885e-cb1258d269fa_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_019c76d5-3dc0-7482-a9e2-6fa63e27b11b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeStatementLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_019c76d5-3dc0-774a-885e-cb1258d269fa" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_019c76d5-3dc0-7482-a9e2-6fa63e27b11b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_OtherRevenuesFromOperationsMember_019c76d5-3dc0-7a0a-b3bb-15a9db5c0bda" xlink:href="mtb-20260331.xsd#mtb_OtherRevenuesFromOperationsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_019c76d5-3dc0-7482-a9e2-6fa63e27b11b" xlink:to="loc_mtb_OtherRevenuesFromOperationsMember_019c76d5-3dc0-7a0a-b3bb-15a9db5c0bda" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_019c76d5-3dc0-7161-ab50-ff743156914d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivablePortfolioSegmentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_019c76d5-3dc0-76a2-be89-ea21563fcba3" xlink:to="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_019c76d5-3dc0-7161-ab50-ff743156914d" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019c76d5-3dc0-7161-ab50-ff743156914d_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivablePortfolioSegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_019c76d5-3dc0-7161-ab50-ff743156914d" xlink:to="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019c76d5-3dc0-7161-ab50-ff743156914d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019c76d5-3dc0-70b4-b289-d0a2c79c4c3f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivablePortfolioSegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_019c76d5-3dc0-7161-ab50-ff743156914d" xlink:to="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019c76d5-3dc0-70b4-b289-d0a2c79c4c3f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommercialPortfolioSegmentMember_019c76d5-3dc0-7f00-b33b-4c7fad46056a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommercialPortfolioSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_019c76d5-3dc0-70b4-b289-d0a2c79c4c3f" xlink:to="loc_us-gaap_CommercialPortfolioSegmentMember_019c76d5-3dc0-7f00-b33b-4c7fad46056a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_CounterpartyNameAxis_019c76d5-3dc0-7d54-b109-cfbafc9fb7a5" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_CounterpartyNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_019c76d5-3dc0-76a2-be89-ea21563fcba3" xlink:to="loc_srt_CounterpartyNameAxis_019c76d5-3dc0-7d54-b109-cfbafc9fb7a5" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RepurchaseAgreementCounterpartyNameDomain_019c76d5-3dc0-7d54-b109-cfbafc9fb7a5_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RepurchaseAgreementCounterpartyNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_CounterpartyNameAxis_019c76d5-3dc0-7d54-b109-cfbafc9fb7a5" xlink:to="loc_srt_RepurchaseAgreementCounterpartyNameDomain_019c76d5-3dc0-7d54-b109-cfbafc9fb7a5_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RepurchaseAgreementCounterpartyNameDomain_019c76d5-3dc0-7a10-8f2b-d4484ebbac66" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RepurchaseAgreementCounterpartyNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_CounterpartyNameAxis_019c76d5-3dc0-7d54-b109-cfbafc9fb7a5" xlink:to="loc_srt_RepurchaseAgreementCounterpartyNameDomain_019c76d5-3dc0-7a10-8f2b-d4484ebbac66" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_BayviewFinancialMember_019c76d5-3dc0-7cc3-b4da-1181698421b9" xlink:href="mtb-20260331.xsd#mtb_BayviewFinancialMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RepurchaseAgreementCounterpartyNameDomain_019c76d5-3dc0-7a10-8f2b-d4484ebbac66" xlink:to="loc_mtb_BayviewFinancialMember_019c76d5-3dc0-7cc3-b4da-1181698421b9" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityMethodInvestmentOwnershipPercentage_019c76d5-3dc0-701e-8675-2c5cfcbdfdac" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EquityMethodInvestmentOwnershipPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019c76d5-3dc0-700a-9056-fc82a40a2a84" xlink:to="loc_us-gaap_EquityMethodInvestmentOwnershipPercentage_019c76d5-3dc0-701e-8675-2c5cfcbdfdac" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityMethodInvestments_019c76d5-3dc0-732b-b2a1-c6cbfe8fa793" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EquityMethodInvestments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019c76d5-3dc0-700a-9056-fc82a40a2a84" xlink:to="loc_us-gaap_EquityMethodInvestments_019c76d5-3dc0-732b-b2a1-c6cbfe8fa793" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeLossFromEquityMethodInvestments_019c76d5-3dc0-7363-8e93-b21034b17aac" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeLossFromEquityMethodInvestments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019c76d5-3dc0-700a-9056-fc82a40a2a84" xlink:to="loc_us-gaap_IncomeLossFromEquityMethodInvestments_019c76d5-3dc0-7363-8e93-b21034b17aac" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_MortgageLoansOfPrivatelyHeldCompany_019c76d5-3dc0-73d8-b387-06b860f505fa" xlink:href="mtb-20260331.xsd#mtb_MortgageLoansOfPrivatelyHeldCompany"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019c76d5-3dc0-700a-9056-fc82a40a2a84" xlink:to="loc_mtb_MortgageLoansOfPrivatelyHeldCompany_019c76d5-3dc0-73d8-b387-06b860f505fa" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_019c76d5-3dc0-7997-9bae-005430d7e104" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019c76d5-3dc0-700a-9056-fc82a40a2a84" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_019c76d5-3dc0-7997-9bae-005430d7e104" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_SubServicedResidentialMortgageLoansOfPrivatelyHeldCompany_019c76d5-3dc0-756c-8beb-e8d465cb5902" xlink:href="mtb-20260331.xsd#mtb_SubServicedResidentialMortgageLoansOfPrivatelyHeldCompany"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019c76d5-3dc0-700a-9056-fc82a40a2a84" xlink:to="loc_mtb_SubServicedResidentialMortgageLoansOfPrivatelyHeldCompany_019c76d5-3dc0-756c-8beb-e8d465cb5902" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_RevenuesFromSubservicing_019c76d5-3dc0-7034-bb6e-28d58a28cef7" xlink:href="mtb-20260331.xsd#mtb_RevenuesFromSubservicing"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019c76d5-3dc0-700a-9056-fc82a40a2a84" xlink:to="loc_mtb_RevenuesFromSubservicing_019c76d5-3dc0-7034-bb6e-28d58a28cef7" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MortgageBackedSecuritiesHeldToMaturityFairValueDisclosure_019c76d5-3dc0-7f0c-84f8-631776bc7bf6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_MortgageBackedSecuritiesHeldToMaturityFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019c76d5-3dc0-700a-9056-fc82a40a2a84" xlink:to="loc_us-gaap_MortgageBackedSecuritiesHeldToMaturityFairValueDisclosure_019c76d5-3dc0-7f0c-84f8-631776bc7bf6" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_CommitmentsToExtendCreditAmount_019c76d5-3dc0-7ecb-8706-70f7c8a84a4d" xlink:href="mtb-20260331.xsd#mtb_CommitmentsToExtendCreditAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019c76d5-3dc0-700a-9056-fc82a40a2a84" xlink:to="loc_mtb_CommitmentsToExtendCreditAmount_019c76d5-3dc0-7ecb-8706-70f7c8a84a4d" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherCommitment_019c76d5-3dc0-7ee0-91ea-82ee6deadc5a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherCommitment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019c76d5-3dc0-700a-9056-fc82a40a2a84" xlink:to="loc_us-gaap_OtherCommitment_019c76d5-3dc0-7ee0-91ea-82ee6deadc5a" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Deposits_019c76d5-3dc0-736c-bf7e-aa54c36f33e3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_Deposits"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019c76d5-3dc0-700a-9056-fc82a40a2a84" xlink:to="loc_us-gaap_Deposits_019c76d5-3dc0-736c-bf7e-aa54c36f33e3" xlink:type="arc" order="10"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://xbrl.sec.gov/ecd/role/IndividualsOnly" xlink:type="simple" xlink:href="https://xbrl.sec.gov/ecd/2025/ecd-2025.xsd#IndividualsOnly"/>
  <link:definitionLink xlink:role="http://xbrl.sec.gov/ecd/role/IndividualsOnly" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_ecd_AllIndividualsMember" xlink:href="https://xbrl.sec.gov/ecd/2025/ecd-2025.xsd#ecd_AllIndividualsMember"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_KevinJ.PearsonMember_019d4e7a-c49d-7a5f-a48b-32aa53667cfa" xlink:href="mtb-20260331.xsd#mtb_KevinJ.PearsonMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ecd_AllIndividualsMember" xlink:to="loc_mtb_KevinJ.PearsonMember_019d4e7a-c49d-7a5f-a48b-32aa53667cfa" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_TracyS.WoodrowMember_019d4e78-e267-7bf1-b7af-f6dbb8c29a62" xlink:href="mtb-20260331.xsd#mtb_TracyS.WoodrowMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ecd_AllIndividualsMember" xlink:to="loc_mtb_TracyS.WoodrowMember_019d4e78-e267-7bf1-b7af-f6dbb8c29a62" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://xbrl.sec.gov/ecd/role/TradingArrangementsOnly" xlink:type="simple" xlink:href="https://xbrl.sec.gov/ecd/2025/ecd-2025.xsd#TradingArrangmentsOnly"/>
  <link:definitionLink xlink:role="http://xbrl.sec.gov/ecd/role/TradingArrangementsOnly" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_ecd_AllTradingArrangementsMember" xlink:href="https://xbrl.sec.gov/ecd/2025/ecd-2025.xsd#ecd_AllTradingArrangementsMember"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_KevinJ.PearsonRuleTradingArrangementCommonStockMember_019d4e7f-190a-7630-afc8-8499908156b3" xlink:href="mtb-20260331.xsd#mtb_KevinJ.PearsonRuleTradingArrangementCommonStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ecd_AllTradingArrangementsMember" xlink:to="loc_mtb_KevinJ.PearsonRuleTradingArrangementCommonStockMember_019d4e7f-190a-7630-afc8-8499908156b3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_mtb_KevinJ.PearsonRuleTradingArrangementStockOptionsMember_019d4e7f-570e-7c0c-84f7-43332d20f020" xlink:href="mtb-20260331.xsd#mtb_KevinJ.PearsonRuleTradingArrangementStockOptionsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ecd_AllTradingArrangementsMember" xlink:to="loc_mtb_KevinJ.PearsonRuleTradingArrangementStockOptionsMember_019d4e7f-570e-7c0c-84f7-43332d20f020" xlink:type="arc" order="2"/>
  </link:definitionLink>
</link:linkbase>
