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Proc-Type: 2001,MIC-CLEAR
Originator-Name: webmaster@www.sec.gov
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MIC-Info: RSA-MD5,RSA,
 AXVM8F2uMkW4tsi8zzK3qArqUPKyB1x0+hPa7PGU1nsc4HSSJyi1mzci7ak/qwE6
 yJAn+cNApI9/hwaYWSEz2A==

<SEC-DOCUMENT>0001179110-06-014701.txt : 20060706
<SEC-HEADER>0001179110-06-014701.hdr.sgml : 20060706
<ACCEPTANCE-DATETIME>20060706092847
ACCESSION NUMBER:		0001179110-06-014701
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20060705
FILED AS OF DATE:		20060706
DATE AS OF CHANGE:		20060706

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			ZENITH NATIONAL INSURANCE CORP
		CENTRAL INDEX KEY:			0000109261
		STANDARD INDUSTRIAL CLASSIFICATION:	FIRE, MARINE & CASUALTY INSURANCE [6331]
		IRS NUMBER:				952702776
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		21255 CALIFA ST
		CITY:			WOODLAND HILLS
		STATE:			CA
		ZIP:			91367
		BUSINESS PHONE:		8187131000

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			VANGUNDY KARI
		CENTRAL INDEX KEY:			0001212531

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-09627
		FILM NUMBER:		06946527

	BUSINESS ADDRESS:	
		BUSINESS PHONE:		9163518515

	MAIL ADDRESS:	
		STREET 1:		C/O GENCORP INC.,
		STREET 2:		P.O. BOX 537012
		CITY:			SACRAMENTO
		STATE:			CA
		ZIP:			95853-7012

	FORMER NAME:	
		FORMER CONFORMED NAME:	VAN GUNDY KARI
		DATE OF NAME CHANGE:	20030110

	FORMER NAME:	
		FORMER CONFORMED NAME:	GUNDY KARI VAN
		DATE OF NAME CHANGE:	20021231
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>edgar.xml
<DESCRIPTION>FORM 4 -
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0202</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2006-07-05</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0000109261</issuerCik>
        <issuerName>ZENITH NATIONAL INSURANCE CORP</issuerName>
        <issuerTradingSymbol>ZNT</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001212531</rptOwnerCik>
            <rptOwnerName>VANGUNDY KARI</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>21255 CALIFA ST.</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>WOODLAND HILLS</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>91367</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>Sr. Vice President</officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2006-07-05</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>10000</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>10522.0682</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>582</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>See Footnote</value>
                    <footnoteId id="F1"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
    </nonDerivativeTable>

    <derivativeTable></derivativeTable>

    <footnotes>
        <footnote id="F1">Represents the approximate number of shares allocated to the reporting person's account in The Zenith 401(k) Plan as of June 28, 2006, the latest practible date for which such information is available.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/ Kari L. Van Gundy</signatureName>
        <signatureDate>2006-07-05</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
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