Yarnbury Castle is the site of a multiphase, multivallate iron age hillfort near the village and civil parish of Steeple Langford, two miles along the A303 from Winterbourne Stoke, in Wiltshire. The site covers an area of 28.5 acres (11.5 ha), and has been extensively surveyed and investigated by the Royal Commission on the Historical Monuments of England (RCHME) in 1991, with finds of iron age and Romano-British pottery, iron age and Roman coins, and burials of human remains.