Martin and Tidpit Downs is a 367.5-hectare (908-acre) biological Site of Special Scientific Interest north-west of Fordingbridge in Hampshire.

[4] Bokerley Dyke, a prehistoric linear earthwork and scheduled monument, runs through the site.

[5] This site is rich in prehistoric earthworks, including Bokerley Dyke.

It has chalk grassland, heath and scrub, with a rich herb flora.

There is an outstanding assemblage of butterflies, with 36 species recorded, including marbled white, dark green fritillary, silver-spotted skipper and Duke of Burgundy.