Barnham Cross Common is a 69.1-hectare (171-acre) biological Site of Special Scientific Interest on the southern outskirts of Thetford in Norfolk. It is owned by Thetford Town Council and is registered common land. It is also a Local Nature Reserve and a Nature Conservation Review site, Grade 1. It is part of the Breckland Special Area of Conservation and Special Protection Area.

This grassland and heath common has diverse habitats and a rich flora, including several nationally rare plants. There are nearly a hundred species of birds, including sixty which breed on the site, and a wide range of invertebrates.

The common is open to the public.