Chanctonbury Hill is an 82.7-hectare (204-acre) biological Site of Special Scientific Interest west of Steyning in West Sussex. Part of it is Chanctonbury Ring, an early Iron Age hillfort which contains two Romano-Celtic temples and which is a Scheduled Monument.

This site on the steep slope of the South Downs is mainly woodland with some areas of chalk grassland. A dew pond has great crested newts, a species protected under the Wildlife and Countryside Act 1981. More than sixty species of breeding birds have been recorded, including meadow pipits, corn buntings and green woodpeckers.