Chanctonbury Ring is a prehistoric hill fort atop Chanctonbury Hill on the South Downs, on the border of the civil parishes of Washington and Wiston in the English county of West Sussex. A ridgeway, now part of the South Downs Way, runs along the hill. It forms part of an ensemble of associated historical features created over a span of more than 2,000 years, including round barrows dating from the Bronze Age to the Saxon periods and dykes dating from the Iron Age and Roman periods.

The South Downs are a range of chalk hills in the south-eastern coastal counties of England that extends for about 260 sq mi (670 km2) across the south-eastern coastal counties of England from the Itchen valley of Hampshire in the west to Beachy Head, in the Eastbourne Downland Estate, East Sussex, in the east. The Downs are bounded on the northern side by a steep escarpment, from whose crest there are extensive views northwards across the Weald. The South Downs National Park forms a much larger area than the chalk range of the South Downs, and includes large parts of the Weald.