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

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2021-11-08</periodOfReport>

    <issuer>
        <issuerCik>0000038777</issuerCik>
        <issuerName>FRANKLIN RESOURCES INC</issuerName>
        <issuerTradingSymbol>BEN</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001725846</rptOwnerCik>
            <rptOwnerName>Plafker Jed A.</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O FRANKLIN RESOURCES, INC.</rptOwnerStreet1>
            <rptOwnerStreet2>ONE FRANKLIN PARKWAY</rptOwnerStreet2>
            <rptOwnerCity>SAN MATEO</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>94403-1906</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isOfficer>1</isOfficer>
            <officerTitle>Executive Vice President</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock, par value $.10</value>
            </securityTitle>
            <transactionDate>
                <value>2021-11-08</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness></transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>23783</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>35.74</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>135389.786</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock, par value $.10</value>
            </securityTitle>
            <transactionDate>
                <value>2021-11-08</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness></transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>15707</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <footnoteId id="F2"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>151096.786</value>
                    <footnoteId id="F3"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock, par value $.10</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>579.1257</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By 401(k)</value>
                    <footnoteId id="F4"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">On November 1, 2019 and November 5, 2020, the Reporting Person was granted certain restricted stock units subject to vesting over a three-year period based upon satisfaction of certain performance criteria. On November 8, 2021, the Issuer's Compensation Committee certified that certain performance criteria with respect to the Issuer's fiscal year ended September 30, 2021 were achieved, and therefore the amount of shares reported in Column 4 are scheduled to vest on December 1, 2021.</footnote>
        <footnote id="F2">Not applicable.</footnote>
        <footnote id="F3">Of the amount of securities beneficially owned, 67,999 shares represent unvested restricted stock and stock unit awards (which excludes the restricted stock units scheduled to vest on December 1, 2021 as reported in Footnote 1).</footnote>
        <footnote id="F4">Reporting Person holds shares in the Franklin Templeton 401(k) Retirement Plan. Information is based on a plan statement as of October 31, 2021.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/ Virginia Rosas, Attorney-in-Fact</signatureName>
        <signatureDate>2021-11-10</signatureDate>
    </ownerSignature>
</ownershipDocument>
