Vestfold County Municipality (Norwegian: Vestfold fylkeskommune) was the regional governing administration of the old Vestfold county in Norway. The county municipality was established in its most recent form on 1 January 1976 when the law was changed to allow elected county councils in Norway. The county municipality was dissolved on 1 January 2020, when Vestfold was merged with the neighboring Telemark county, creating the new Viken county which is led by the Viken County Municipality. The administrative seat is located in Tønsberg and the county mayor was of the Conservative Party and the final chief administrative officer for the county municipality was Egil Johansen.