TSM: Hou Yung-Chin reported employee-plan purchases

<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0609</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2026-10-07</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001046179</issuerCik>
        <issuerName>TAIWAN SEMICONDUCTOR MANUFACTURING CO LTD</issuerName>
        <issuerTradingSymbol>TSM</issuerTradingSymbol>
        <issuerForeignTradingSymbol>2330.TW</issuerForeignTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0002113680</rptOwnerCik>
            <rptOwnerName>Hou Yung-Chin</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerNonUSAddressFlag>true</rptOwnerNonUSAddressFlag>
            <rptOwnerStreet1>NO. 8, LI-HSIN ROAD 6</rptOwnerStreet1>
            <rptOwnerStreet2>HSINCHU SCIENCE PARK</rptOwnerStreet2>
            <rptOwnerCity>HSINCHU</rptOwnerCity>
            <rptOwnerNonUSStateTerritory>TAIWAN</rptOwnerNonUSStateTerritory>
            <rptOwnerCountry>F5</rptOwnerCountry>
            <rptOwnerZipCode>300096</rptOwnerZipCode>
            <rptOwnerStateDescription>TAIWAN</rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>SVP and Deputy Co-COO</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <aff10b5One>0</aff10b5One>

    <nonDerivativeTable>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Shares (2330.TW)</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>710427</value>
                    <footnoteId id="F1"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Shares (2330.TW)</value>
            </securityTitle>
            <transactionDate>
                <value>2026-10-07</value>
                <footnoteId id="F2"/>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>P</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>60</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>79.39</value>
                    <footnoteId id="F3"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>60</value>
                    <footnoteId id="F1"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By ESPP Trust</value>
                    <footnoteId id="F4"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Shares (2330.TW)</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>60802</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By Spouse</value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
    </nonDerivativeTable>

    <derivativeTable></derivativeTable>

    <footnotes>
        <footnote id="F1">On September 30, 2026, 7,521 and 20,190 Common Shares previously held indirectly through the ESPP Trust and LTI Trust, respectively, were transferred to an account directly held by the reporting person. These transfers reflect only a change in the form of beneficial ownership of the shares and are exempt from reporting under Rule 16a-13 of the Securities Exchange Act of 1934, as amended.</footnote>
        <footnote id="F2">Common Shares purchased by the administrator of the issuer's Employee Stock Purchase Plan (&quot;ESPP&quot;) on behalf of the filer pursuant to terms predetermined by the issuer.</footnote>
        <footnote id="F3">The price was translated from the average purchase price of NT$2,524.2277 in New Taiwan dollars, at the rate of NT$31.795 to US$1.</footnote>
        <footnote id="F4">Common Shares purchased and held under the issuer's Employee Stock Purchase Plan (&quot;ESPP&quot;).</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/ Jen-Chau Huang, as attorney-in-fact</signatureName>
        <signatureDate>2026-10-08</signatureDate>
    </ownerSignature>
</ownershipDocument>