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

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2019-08-16</periodOfReport>

    <notSubjectToSection16>1</notSubjectToSection16>

    <issuer>
        <issuerCik>0001398659</issuerCik>
        <issuerName>Genpact LTD</issuerName>
        <issuerTradingSymbol>G</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001040508</rptOwnerCik>
            <rptOwnerName>BAIN CAPITAL INVESTORS LLC</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>200 CLARENDON STREET</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>BOSTON</rptOwnerCity>
            <rptOwnerState>MA</rptOwnerState>
            <rptOwnerZipCode>02116</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001520731</rptOwnerCik>
            <rptOwnerName>Bain Capital Partners Asia II, L.P.</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>200 CLARENDON STREET</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>BOSTON</rptOwnerCity>
            <rptOwnerState>MA</rptOwnerState>
            <rptOwnerZipCode>02116</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001525871</rptOwnerCik>
            <rptOwnerName>Bain Capital Partners X, L.P.</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>200 CLARENDON STREET</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>BOSTON</rptOwnerCity>
            <rptOwnerState>MA</rptOwnerState>
            <rptOwnerZipCode>02116</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001561353</rptOwnerCik>
            <rptOwnerName>BCIP Associates IV, L.P.</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>200 CLARENDON STREET</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>BOSTON</rptOwnerCity>
            <rptOwnerState>MA</rptOwnerState>
            <rptOwnerZipCode>02116</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001561352</rptOwnerCik>
            <rptOwnerName>BCIP Associates IV-B, L.P.</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>200 CLARENDON STREET</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>BOSTON</rptOwnerCity>
            <rptOwnerState>MA</rptOwnerState>
            <rptOwnerZipCode>02116</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001561186</rptOwnerCik>
            <rptOwnerName>Glory Investments A Ltd</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>200 CLARENDON STREET</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>BOSTON</rptOwnerCity>
            <rptOwnerState>MA</rptOwnerState>
            <rptOwnerZipCode>02116</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001561183</rptOwnerCik>
            <rptOwnerName>Glory Investments B Ltd</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>200 CLARENDON STREET</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>BOSTON</rptOwnerCity>
            <rptOwnerState>MA</rptOwnerState>
            <rptOwnerZipCode>02116</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001561182</rptOwnerCik>
            <rptOwnerName>Glory Investments IV Ltd</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>200 CLARENDON STREET</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>BOSTON</rptOwnerCity>
            <rptOwnerState>MA</rptOwnerState>
            <rptOwnerZipCode>02116</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001561181</rptOwnerCik>
            <rptOwnerName>Glory Investments IV-B Ltd</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>200 CLARENDON STREET</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>BOSTON</rptOwnerCity>
            <rptOwnerState>MA</rptOwnerState>
            <rptOwnerZipCode>02116</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Shares</value>
            </securityTitle>
            <transactionDate>
                <value>2019-08-16</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>S</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>10621804</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>40.51</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>12916004</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>See footnotes</value>
                    <footnoteId id="F1"/>
                    <footnoteId id="F2"/>
                    <footnoteId id="F3"/>
                    <footnoteId id="F4"/>
                    <footnoteId id="F5"/>
                    <footnoteId id="F6"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">Bain Capital Partners Asia II, L.P. (&quot;Asia II&quot;) is the Class A shareholder of Glory Investments A Limited (&quot;Glory A&quot;). As a result, Asia II may be deemed to beneficially own Common Shares held by Glory A. Asia II disclaims beneficial ownership of such securities except to the extent of its pecuniary interest therein. On August 16, 2019, Glory A sold 2,957,962 Common Shares. Following such sale, Glory A held 3,596,840 Common Shares.</footnote>
        <footnote id="F2">Bain Capital Partners X, L.P. (&quot;BCP X&quot;) is the Class A shareholder of Glory Investments B Limited (&quot;Glory B&quot;). As a result, BCP X may be deemed to beneficially own Common Shares held by Glory B. BCP X disclaims beneficial ownership of such securities except to the extent of its pecuniary interest therein. On August 16, 2019, Glory B sold 7,293,590 Common Shares. Following such sale, Glory B held 8,868,930 Common Shares</footnote>
        <footnote id="F3">On August 16, 2019, Glory Investments IV Limited (&quot;Glory IV&quot;), whose Class A shareholder is BCIP Associates IV, L.P. (&quot;BCIP IV&quot;), whose general partner is Boylston Coinvestors, LLC (&quot;Boylston&quot;), sold 344,326 Common Shares. Following such sale, Glory IV held 418,700 Common Shares. BCIP IV may be deemed to beneficially own Common Shares held by Glory IV. BCIP IV disclaims beneficial ownership of such securities except to the extent of its pecuniary interest therein.</footnote>
        <footnote id="F4">On August 16, 2019, Glory Investments IV-B Limited (&quot;Glory IV-B&quot; and together with Glory A, Glory B and Glory IV, the &quot;Bain Capital Entities&quot;), whose Class A shareholder is BCIP Associates IV-B, L.P. (&quot;BCIP IV-B&quot;), whose general partner is Boylston, sold 25,926 shares of Common Stock. Following such sale, Glory IV-B held 31,534 Common Shares. BCIP IV-B may be deemed to beneficially own Common Shares held by Glory IV-B. BCIP IV-B disclaims beneficial ownership of such securities except to the extent of its pecuniary interest therein.</footnote>
        <footnote id="F5">Bain Capital Investors, LLC (&quot;BCI&quot;) is the general partner of Asia II and BCP X and governs the investment strategy and decision-making process with respect to investments held by Glory IV and Glory IV-B.</footnote>
        <footnote id="F6">By virtue of the relationships described in these footnotes, BCI may be deemed to share voting and dispositive power with respect to the Common Shares held by the Bain Capital Entities. BCI disclaims beneficial ownership of such securities except to the extent of its pecuniary interest therein.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>BAIN CAPITAL INVESTORS, LLC, By: /s/ David Humphrey, Name: David Humphrey, Title: Managing Director</signatureName>
        <signatureDate>2019-08-19</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>BAIN CAPITAL PARTNERS ASIA II, L.P., BY: BAIN CAPITAL INVESTORS, LLC, its general partner, By: /s/ David Humphrey, Name: David Humphrey, Title: Managing Director</signatureName>
        <signatureDate>2019-08-19</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>BAIN CAPITAL PARTNERS X, L.P., BY: BAIN CAPITAL INVESTORS, LLC, its general partner, By: /s/ David Humphrey, Name: David Humphrey, Title: Managing Director</signatureName>
        <signatureDate>2019-08-19</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>BCIP ASSOCIATES IV, L.P., BY: BOYLSTON COINVESTORS, LLC, its general partner, By: /s/ David Humphrey, Name: David Humphrey, Title: Authorized Signatory</signatureName>
        <signatureDate>2019-08-19</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>BCIP ASSOCIATES IV-B, L.P., BY: BOYLSTON COINVESTORS, LLC, its general partner, By: /s/ David Humphrey, Name: David Humphrey, Title: Authorized Signatory</signatureName>
        <signatureDate>2019-08-19</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>GLORY INVESTMENTS A LIMITED, By: /s/ James Hildebrandt, Name: James Hildebrandt, Title: Director</signatureName>
        <signatureDate>2019-08-19</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>GLORY INVESTMENTS B LIMITED, By: /s/ James Hildebrandt, Name: James Hildebrandt, Title: Director</signatureName>
        <signatureDate>2019-08-19</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>GLORY INVESTMENTS IV LIMITED, By: /s/ James Hildebrandt, Name: James Hildebrandt, Title: Director</signatureName>
        <signatureDate>2019-08-19</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>GLORY INVESTMENTS IV-B LIMITED, By: /s/ James Hildebrandt, Name: James Hildebrandt, Title: Director</signatureName>
        <signatureDate>2019-08-19</signatureDate>
    </ownerSignature>
</ownershipDocument>
