Wallingford Castle was a major medieval castle situated in Wallingford in the English county of Oxfordshire (historically in Berkshire until the 1974 reorganisation), adjacent to the River Thames. Established in the 11th century as a motte-and-bailey design within an Anglo-Saxon burgh, it grew to become what historian Nicholas Brooks has described as "one of the most powerful royal castles of the 12th and 13th centuries".