Martham Broad is a National Nature Reserve in Norfolk, covering 0.62 km². It is one of 20 National Nature Reserves in the county. Only two are smaller. The surrounding countryside is part of the Broads National Park.
The nearest railway station is Acle, about 11.4 km to the south-west. Winterton Dunes and Ludham & Potter Heigham Marshes are among the National Nature Reserves within 4.7 km.