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

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2021-12-21</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001653384</issuerCik>
        <issuerName>Runway Growth Finance Corp.</issuerName>
        <issuerTradingSymbol>RWAY</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>0001861643</rptOwnerCik>
            <rptOwnerName>BAM Partners Trust</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>BROOKFIELD PLACE, SUITE 300</rptOwnerStreet1>
            <rptOwnerStreet2>181 BAY ST. PO BOX 762</rptOwnerStreet2>
            <rptOwnerCity>TORONTO, ONTARIO</rptOwnerCity>
            <rptOwnerState>A6</rptOwnerState>
            <rptOwnerZipCode>M5J 2T3</rptOwnerZipCode>
            <rptOwnerStateDescription>ONTARIO, CANADA</rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001001085</rptOwnerCik>
            <rptOwnerName>BROOKFIELD ASSET MANAGEMENT INC.</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>BROOKFIELD PLACE, SUITE 300</rptOwnerStreet1>
            <rptOwnerStreet2>181 BAY ST. P.O. BOX 762</rptOwnerStreet2>
            <rptOwnerCity>TORONTO, ONTARIO</rptOwnerCity>
            <rptOwnerState>A6</rptOwnerState>
            <rptOwnerZipCode>M5J 2T3</rptOwnerZipCode>
            <rptOwnerStateDescription>ONTARIO, CANADA</rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</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>C/O OAKTREE CAPITAL MANAGEMENT, L.P.</rptOwnerStreet1>
            <rptOwnerStreet2>333 SOUTH GRAND AVENUE, 28TH FLOOR</rptOwnerStreet2>
            <rptOwnerCity>LOS ANGELES</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>90071</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</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>C/O OAKTREE CAPITAL MANAGEMENT, L.P.</rptOwnerStreet1>
            <rptOwnerStreet2>333 SOUTH GRAND AVENUE, 28TH FLOOR</rptOwnerStreet2>
            <rptOwnerCity>LOS ANGELES</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>90071</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</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>C/O OAKTREE CAPITAL MANAGEMENT, L.P.</rptOwnerStreet1>
            <rptOwnerStreet2>333 SOUTH GRAND AVENUE, 28TH FLOOR</rptOwnerStreet2>
            <rptOwnerCity>LOS ANGELES</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>90071</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</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>C/O OAKTREE CAPITAL MANAGEMENT, L.P.</rptOwnerStreet1>
            <rptOwnerStreet2>333 SOUTH GRAND AVENUE, 28TH FLOOR</rptOwnerStreet2>
            <rptOwnerCity>LOS ANGELES</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>90071</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</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>C/O OAKTREE CAPITAL MANAGEMENT, L.P.</rptOwnerStreet1>
            <rptOwnerStreet2>333 SOUTH GRAND AVENUE, 28TH FLOOR</rptOwnerStreet2>
            <rptOwnerCity>LOS ANGELES</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>90071</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</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>C/O OAKTREE CAPITAL MANAGEMENT, L.P.</rptOwnerStreet1>
            <rptOwnerStreet2>333 SOUTH GRAND AVENUE, 28TH FLOOR</rptOwnerStreet2>
            <rptOwnerCity>LOS ANGELES</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>90071</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</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>C/O OAKTREE CAPITAL MANAGEMENT, L.P.</rptOwnerStreet1>
            <rptOwnerStreet2>333 SOUTH GRAND AVENUE, 28TH FLOOR</rptOwnerStreet2>
            <rptOwnerCity>LOS ANGELES</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>90071</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</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>2021-12-21</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>P</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>21325</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>13.4195</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>19817090</value>
                    <footnoteId id="F1"/>
                    <footnoteId id="F7"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                    <footnoteId id="F2"/>
                    <footnoteId id="F3"/>
                    <footnoteId id="F4"/>
                    <footnoteId id="F5"/>
                    <footnoteId id="F6"/>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock, par value $0.01 per share</value>
            </securityTitle>
            <transactionDate>
                <value>2021-12-22</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>P</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>21570</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>13.363</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>19838660</value>
                    <footnoteId id="F7"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                    <footnoteId id="F2"/>
                    <footnoteId id="F3"/>
                    <footnoteId id="F4"/>
                    <footnoteId id="F5"/>
                    <footnoteId id="F6"/>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock, par value $0.01 per share</value>
            </securityTitle>
            <transactionDate>
                <value>2021-12-23</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>P</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>20010</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>13.3389</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>19858760</value>
                    <footnoteId id="F7"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                    <footnoteId id="F2"/>
                    <footnoteId id="F3"/>
                    <footnoteId id="F4"/>
                    <footnoteId id="F5"/>
                    <footnoteId id="F6"/>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">Includes shares acquired pursuant to the issuer's dividend reinvestment plan.</footnote>
        <footnote id="F2">OCM Growth Holdings, LLC, a Delaware limited liability company (&quot;LLC&quot;)(&quot;OCMGH&quot;), directly owns 14,933,309.96 shares of the common stock (the &quot;Common Stock&quot;) of Runway Growth Finance Corp. (&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 LLC, (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="F3">(Continued from Footnote 2) 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 the indirect owner of the class B units of OCG; (viii) Brookfield Asset Management Inc., a Canadian corporation (&quot;BAM&quot;), in its capacity as the indirect owner of the class A units of OCG; and (ix) BAM Partners Trust, a trust formed under the laws of Ontario, in its capacity as the sole owner of Class B Limited Voting Shares of BAM..</footnote>
        <footnote id="F4">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="F5">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="F6">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>
        <footnote id="F7">This transaction was effected pursuant to a Rule 10b-5 plan adopted by the Reporting Persons</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/ Henry Orren, Senior Vice President</signatureName>
        <signatureDate>2021-12-23</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>Oaktree Fund GP, LLC, By: Oaktree Fund GP I, L.P. Its Managing Member, /s/ Henry Orren, Senior Vice President</signatureName>
        <signatureDate>2021-12-23</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>Oaktree Fund GP I, L.P., /s/ Henry Orren, Senior Vice President</signatureName>
        <signatureDate>2021-12-23</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>Oaktree Capital I, L.P., /s/ Henry Orren, Senior Vice President</signatureName>
        <signatureDate>2021-12-23</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>OCM Holdings I, LLC, /s/ Henry Orren, Senior Vice President</signatureName>
        <signatureDate>2021-12-23</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>Oaktree Holdings, LLC, /s/ Henry Orren, Senior Vice President</signatureName>
        <signatureDate>2021-12-23</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>Oaktree Capital Group, LLC, By: Oaktree Capital Group Holdings GP, LLC Its Manager, /s/ Henry Orren, Senior Vice President</signatureName>
        <signatureDate>2021-12-23</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>Oaktree Capital Group Holdings, L.P., By: Oaktree Capital Group Holdings GP, LLC Its: General Partner, /s/ Henry Orren, Senior Vice President</signatureName>
        <signatureDate>2021-12-23</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>Brookfield Asset Management, /s/ Kathy Sarpash, Senior Vice President, Legal &amp; Regulatory</signatureName>
        <signatureDate>2021-12-23</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>BAM Partners Trust, /s/ Kathy Sarpash, Secretary</signatureName>
        <signatureDate>2021-12-23</signatureDate>
    </ownerSignature>
</ownershipDocument>
