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

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2017-07-25</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0000704051</issuerCik>
        <issuerName>LEGG MASON, INC.</issuerName>
        <issuerTradingSymbol>LM</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001677229</rptOwnerCik>
            <rptOwnerName>Chen Tian Qiao</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>8 STEVENS ROAD</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>SINGAPORE</rptOwnerCity>
            <rptOwnerState>U0</rptOwnerState>
            <rptOwnerZipCode>257819</rptOwnerZipCode>
            <rptOwnerStateDescription>SINGAPORE</rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001318400</rptOwnerCik>
            <rptOwnerName>Shanda Media LTD</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>NO. 1 OFFICE BUILDING, NO. 690</rptOwnerStreet1>
            <rptOwnerStreet2>PUDONG, NEW AREA</rptOwnerStreet2>
            <rptOwnerCity>SHANGHAI</rptOwnerCity>
            <rptOwnerState>F4</rptOwnerState>
            <rptOwnerZipCode>201203</rptOwnerZipCode>
            <rptOwnerStateDescription>CHINA</rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001633666</rptOwnerCik>
            <rptOwnerName>Shanda Investment Group Ltd</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>FIRST REGISTER OFFICE</rptOwnerStreet1>
            <rptOwnerStreet2>WOODBOURNE HALL, ROAD TOWN</rptOwnerStreet2>
            <rptOwnerCity>TORTOLA</rptOwnerCity>
            <rptOwnerState>D8</rptOwnerState>
            <rptOwnerZipCode>00000</rptOwnerZipCode>
            <rptOwnerStateDescription>VIRGIN ISLANDS, BRITISH</rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001633667</rptOwnerCik>
            <rptOwnerName>Shanda Technology Overseas Capital Co.</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>REGISTERED OFFICE, CRICKET SQUARE</rptOwnerStreet1>
            <rptOwnerStreet2>HUTCHINS DRIVE, PO BOX 2681</rptOwnerStreet2>
            <rptOwnerCity>GRAND CAYMAN</rptOwnerCity>
            <rptOwnerState>E9</rptOwnerState>
            <rptOwnerZipCode>KY1-1111</rptOwnerZipCode>
            <rptOwnerStateDescription>CAYMAN ISLANDS</rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001672562</rptOwnerCik>
            <rptOwnerName>Shanda Asset Management Investment Ltd</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>8 STEVENS ROAD</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>SINGAPORE</rptOwnerCity>
            <rptOwnerState>U0</rptOwnerState>
            <rptOwnerZipCode>257819</rptOwnerZipCode>
            <rptOwnerStateDescription>SINGAPORE</rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
                <footnoteId id="F1"/>
            </securityTitle>
            <transactionDate>
                <value>2017-07-25</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>3041</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>6424</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>5567653</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>See Footnote</value>
                    <footnoteId id="F2"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">Common Stock granted pursuant to and under the conditions of the Legg Mason, Inc. Non-Employee Director Equity Plan, as amended. See Appendix A to the definitive proxy statement for Legg Mason, Inc.'s 2013 Annual Meeting of Stockholders.</footnote>
        <footnote id="F2">These shares of Common Stock are directly held by Shanda Asset Management Investment Limited. Mr. Tianqiao Chen is the sole shareholder of Shanda Media Limited.  Shanda Media Limited owns 70% of all outstanding and issued shares of Shanda Investment Group Limited which is the sole shareholder of Shanda Technology Overseas Capital Company Limited. Shanda Technology Overseas Capital Company Limited is the sole shareholder of Shanda Asset Management Investment Limited.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/ Tianqiao Chen</signatureName>
        <signatureDate>2017-07-27</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>/s/ Tianqiao Chen, Director of Shanda Media Limited</signatureName>
        <signatureDate>2017-07-27</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>/s/ Tianqiao Chen, Director of Shanda Investment Group Limited</signatureName>
        <signatureDate>2017-07-27</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>/s/ Tianqiao Chen, Director of Shanda Technology Overseas Capital Company Limited</signatureName>
        <signatureDate>2017-07-27</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>/s/ Tianqiao Chen, Director of Shanda Asset Management Investment Limited</signatureName>
        <signatureDate>2017-07-27</signatureDate>
    </ownerSignature>
</ownershipDocument>
