King John's Palace is a ruined Norman merchant's house in Southampton, England. Incorrectly believed for a period to have been used by King John, resulting in its modern name, the west wall of the house was converted to form part of the city's defensive walls in the early 14th century and its archways contain what may be Britain's earliest surviving gunports. The structure now forms part of the Tudor House Museum in the city and is a Scheduled Ancient Monument.