The South Downs National Park is England's newest National Park, having become fully operational on 1 April 2011. The park, covering an area of 1,627 square kilometres (628 sq mi) in southern England, stretches for 140 kilometres (87 mi) from Winchester in the west to Eastbourne in the east through the counties of Hampshire, West Sussex and East Sussex.

The national park covers not only the chalk ridge of the South Downs, with its celebrated chalk downland landscape that culminates in the iconic chalky white cliffs of Beachy Head, but also a substantial part of a separate physiographic region, the western Weald, with its heavily wooded sandstone and clay hills and vales. The South Downs Way spans the entire length of the park and is the only National Trail that lies wholly within a national park.