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

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2018-09-14</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001653384</issuerCik>
        <issuerName>Runway Growth Credit Fund Inc.</issuerName>
        <issuerTradingSymbol>NONE</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001693272</rptOwnerCik>
            <rptOwnerName>OCM Growth Holdings LLC</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O OAKTREE CAPITAL MANAGEMENT, L.P.</rptOwnerStreet1>
            <rptOwnerStreet2>333 S. GRAND AVE., 28TH FLOOR</rptOwnerStreet2>
            <rptOwnerCity>LOS ANGELES</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>90071</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001499005</rptOwnerCik>
            <rptOwnerName>Oaktree Fund GP, LLC</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>333 SOUTH GRAND AVENUE, 28TH FLOOR</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>LOS ANGELES</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>90071</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001402746</rptOwnerCik>
            <rptOwnerName>OAKTREE FUND GP I, L.P.</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>333 SOUTH GRAND AVENUE, 28TH FLOOR</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>LOS ANGELES</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>90071</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001403530</rptOwnerCik>
            <rptOwnerName>Oaktree Capital I, L.P.</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>333 SOUTH GRAND AVENUE, 28TH FLOOR</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>LOS ANGELES</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>90071</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001407178</rptOwnerCik>
            <rptOwnerName>OCM HOLDINGS I, LLC</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>333 SOUTH GRAND AVENUE, 28TH FLOOR</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>LOS ANGELES</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>90071</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001407181</rptOwnerCik>
            <rptOwnerName>OAKTREE HOLDINGS, LLC</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>333 SOUTH GRAND AVENUE, 28TH FLOOR</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>LOS ANGELES</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>90071</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001403528</rptOwnerCik>
            <rptOwnerName>Oaktree Capital Group, LLC</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>333 SOUTH GRAND AVENUE, 28TH FLOOR</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>LOS ANGELES</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>90071</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001403525</rptOwnerCik>
            <rptOwnerName>Oaktree Capital Group Holdings GP, LLC</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>333 SOUTH GRAND AVENUE, 28TH FLOOR</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>LOS ANGELES</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>90071</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock, par value $0.01 per share</value>
            </securityTitle>
            <transactionDate>
                <value>2018-09-14</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>P</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>1006898.73</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>15.02</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>5495267.66</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                    <footnoteId id="F1"/>
                    <footnoteId id="F2"/>
                    <footnoteId id="F3"/>
                    <footnoteId id="F4"/>
                    <footnoteId id="F5"/>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">OCM Growth Holdings, LLC, a Delaware limited liability company (&quot;LLC&quot;)(&quot;OCMGH&quot;), directly owns 5,495,267.66 shares of the common stock (the &quot;Common Stock&quot;) of Runway Growth Credit Fund, Inc. (&quot;Issuer&quot;). This Form 4 is being filed by (i) Oaktree Fund GP, LLC, a Delaware LLC (&quot;GP LLC&quot;), in its capacity as manager of OCMGH, (ii) Oaktree GP I, L.P., a Delaware limited partnership (&quot;GP I LLC&quot;), in its capacity as managing member of GP LLP, (iii) Oaktree Capital I, L.P., a Delaware limited partnership (&quot;Capital I&quot;), in its capacity as general partner of GP I, (iv) OCM Holdings I, LLC, a Delaware LLC (&quot;Holdings I&quot;), in its capacity as general partner of Capital I, (v) Oaktree Holdings, LLC, a Delaware LLC (&quot;Holdings&quot;),</footnote>
        <footnote id="F2">(Continued from Footnote 1) in its capacity as managing member of Holdings I; (vi) Oaktree Capital Group, LLC, a Delaware LLC (&quot;OCG&quot;), in its capacity as managing member of Holdings; and (vii) Oaktree Capital Group Holdings GP, LLC, a Delaware LLC (&quot;OCGH GP&quot;), in its capacity as duly elected manager of OCG.</footnote>
        <footnote id="F3">Each Reporting Person disclaims beneficial ownership of all equity securities reported herein except to the extent of its respective pecuniary interest therein, and the filing of this Form 4 shall not be construed as an admission that any such Reporting Person is the beneficial owner of any equity securities covered by this Form 4.</footnote>
        <footnote id="F4">OCGH GP is managed by an executive committee consisting of Howard S. Marks, Bruce A. Karsh, Sheldon M. Stone, John B. Frank, and Jay S. Wintrob (the &quot;OCGH GP Members&quot;). In such capacity, the OCGH GP Members may be deemed to have indirect beneficial ownership of the Common Stock. Each OCGH GP Member expressly disclaims beneficial ownership of the Common Stock, except to the extent of his respective pecuniary interest therein, and the filing of this Form 4 shall not be construed as an admission that any such person is the beneficial owner of any equity securities covered by this Form 4.</footnote>
        <footnote id="F5">The Reporting Persons may be deemed directors by deputization by virtue of their right to designate representatives to be nominated by the Issuer to serve on the Issuer's board of directors.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>OCM Growth Holdings, LLC, By: Oaktree Fund GP, LLC Its: Manager, By: Oaktree Fund GP I, L.P. Its Managing Member, /s/ Jordan Mikes, Authorized Signatory</signatureName>
        <signatureDate>2018-09-18</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>Oaktree Fund GP, LLC, By: Oaktree Fund GP I, L.P. Its Managing Member, /s/ Jordan Mikes, Authorized Signatory</signatureName>
        <signatureDate>2018-09-18</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>Oaktree Fund GP I, L.P., /s/ Jordan Mikes, Authorized Signatory</signatureName>
        <signatureDate>2018-09-18</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>Oaktree Capital I, L.P., /s/ Jordan Mikes, Vice President</signatureName>
        <signatureDate>2018-09-18</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>OCM Holdings I, LLC, /s/ Jordan Mikes, Vice President</signatureName>
        <signatureDate>2018-09-18</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>Oaktree Holdings, LLC, /s/ Jordan Mikes, Vice President</signatureName>
        <signatureDate>2018-09-18</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>Oaktree Capital Group, LLC, By: Oaktree Capital Group Holdings GP, LLC Its Manager, /s/ Jordan Mikes, Vice President</signatureName>
        <signatureDate>2018-09-18</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>Oaktree Capital Group Holdings, L.P., By: Oaktree Capital Group Holdings GP, LLC Its: General Partner, /s/ Jordan Mikes, Vice President</signatureName>
        <signatureDate>2018-09-18</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>Oaktree Capital Group Holdings GP, LLC, /s/ Jordan Mikes, Vice President</signatureName>
        <signatureDate>2018-09-18</signatureDate>
    </ownerSignature>
</ownershipDocument>
