King John's Hill is the site of an Iron Age hillfort located in Hampshire, in southeast England. The hill is situated in the parish of Worldham, in East Hampshire District. It is a Scheduled Ancient Monument with a list entry identification number of 1020314, and a Monument Number of 243207.
King John's Hill is a small multivallate hillfort, a fort with multiple defensive rings, and has been dated on ceramic evidence to approximately 100 BC. It was later reoccupied during the medieval period, with 13th–14th century AD building traces and pottery fragments. These have been identified as the potential remains of a hunting lodge traditionally said to have been built by King John.
The hill rises 129 metres (423 ft) above mean sea level and is just over 0.5 kilometres (0.31 mi) southeast of the village of East Worldham, and approximately 4 kilometres (2.5 mi) east of the town of Alton. The hill falls within the boundaries of the South Downs National Park. It is a greensand tor, with a flat top and steep sides; it is heavily wooded, with dense undergrowth.
The hillfort is unusually small, and its defences were weak; the site falls in a borderline category between larger hillforts and smaller defended settlements. It is oval in shape and encloses an area of appriximately 0.8 hectares (86,000 sq ft). Although it has suffered some damage by malm quarrying, it is still well preserved. Limited archaeological excavation revealed plentiful evidence of the hill's Iron Age occupation, later medieval remains, and post-medieval activity.
The quarrying has destroyed the fort's defences on the north side of the hill, but they are elsewhere evidenced by two concentric scarps separated by a wide shelf. On the northeast side, a ridge line meets the fort, and was cut by a shallow ditch, which meets with a later boundary that runs around the base of the hill on the east side, and encloses a number of terraces on the lower slopes of the hill.