Old Winchester Hill grid reference SU643205 is a chalk hill in Hampshire, England surmounted by an Iron Age hill fort and a Bronze Age cemetery. It is a Site of Special Scientific Interest and a National Nature Reserve. The hill fort has never been fully excavated.
Despite its name the hill is around 11 miles (18 km) from Winchester; it is however part of the Winchester-East Meon Anticline. It lies to the east of Corhampton on the eastern side of the Meon Valley, opposite Beacon Hill. The South Downs Way and Monarch's Way long distance footpaths cross the summit of the hill, which reaches 197 metres (646 ft). About 2 kilometres to the northeast is another prominent hill, Henwood Down (201 m), above the village of East Meon.
In March 2009, it became part of the South Downs National Park.
On the summit of the hill is an Iron Age hill fort. Within the hill fort can also be found Bronze Age barrows. The barrows date from between 4500 and 3,500 BCE whilst the fort itself is believed to be Iron Age in origin. It was probably built in the Early or early-Middle Iron Age (600-300 BCE) and fell out of use around the beginning of the Late Iron Age (150-100 BCE), as this is the general pattern for hillforts in the southeast of England. More modern archaeology dates from World War II when the British Army used the hill as a mortar testing range. Some unexploded Ordnance may still remain in 'fenced-off' sections of the hill however grazing hill-sheep access all areas so danger to the casual walker is likely to be low.