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Proc-Type: 2001,MIC-CLEAR
Originator-Name: webmaster@www.sec.gov
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MIC-Info: RSA-MD5,RSA,
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<SEC-DOCUMENT>0000036966-08-000033.txt : 20080422
<SEC-HEADER>0000036966-08-000033.hdr.sgml : 20080422
<ACCEPTANCE-DATETIME>20080422113518
ACCESSION NUMBER:		0000036966-08-000033
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20080418
FILED AS OF DATE:		20080422
DATE AS OF CHANGE:		20080422

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			FIRST HORIZON NATIONAL CORP
		CENTRAL INDEX KEY:			0000036966
		STANDARD INDUSTRIAL CLASSIFICATION:	NATIONAL COMMERCIAL BANKS [6021]
		IRS NUMBER:				620803242
		STATE OF INCORPORATION:			TN
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		165 MADISON AVENUE
		CITY:			MEMPHIS
		STATE:			TN
		ZIP:			38103
		BUSINESS PHONE:		9018186232

	MAIL ADDRESS:	
		STREET 1:		165 MADISON AVENUE
		CITY:			MEMPHIS
		STATE:			TN
		ZIP:			38103

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	FIRST TENNESSEE NATIONAL CORP
		DATE OF NAME CHANGE:	19920703

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	FIRST TENNESSEE BANKS INC
		DATE OF NAME CHANGE:	19600201

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			HASLAM JAMES A III
		CENTRAL INDEX KEY:			0001224969

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-15185
		FILM NUMBER:		08768588

	BUSINESS ADDRESS:	
		STREET 1:		FIRST TENNESSEE NATIONAL CORP
		STREET 2:		165 MADISON AVENUE
		CITY:			MEMPHIS
		STATE:			TN
		ZIP:			38103
		BUSINESS PHONE:		9015235679

	MAIL ADDRESS:	
		STREET 1:		165 MADISON AVENUE
		CITY:			MEMPHIS
		STATE:			TN
		ZIP:			38103
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>doc.xml
<DESCRIPTION>PRIMARY DOCUMENT
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0202</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2008-04-18</periodOfReport>

    <issuer>
        <issuerCik>0000036966</issuerCik>
        <issuerName>FIRST HORIZON NATIONAL CORP</issuerName>
        <issuerTradingSymbol>FHN</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001224969</rptOwnerCik>
            <rptOwnerName>HASLAM JAMES A III</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>PILOT TRAVEL CENTERS LLC</rptOwnerStreet1>
            <rptOwnerStreet2>5508 LONAS ROAD</rptOwnerStreet2>
            <rptOwnerCity>KNOXVILLE</rptOwnerCity>
            <rptOwnerState>TN</rptOwnerState>
            <rptOwnerZipCode>37909</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle></officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2008-04-18</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F1"/>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>2572</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>22085</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <derivativeTable></derivativeTable>

    <footnotes>
        <footnote id="F1">Grant of restricted stock units which will vest the second Monday in February 2009.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>by John A. Niemoeller, attorney-in-fact</signatureName>
        <signatureDate>2008-04-21</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
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