Martin Down is a National Nature Reserve in Hampshire, covering 3.4 km². It is one of eight National Nature Reserves in the county. It lies within Cranborne Chase and West Wiltshire Downs National Landscape.
For arrivals by rail, Tisbury Station is about 11.8 km to the north-west. Pentridge Down and Chickengrove Bottom are among the nature reserves within 2.1 km.