Mattishall Moor is a 5.5-hectare (14-acre) biological Site of Special Scientific Interest east of Dereham in Norfolk.

This area of calcareous fen and marshy grassland has a rich variety of flora. Black bog-rush, blunt-flowered rush and purple moor-grass are common in the fen areas, and purple moor-grass is also abundant in the grassland, together with other plants such as yellow rattle and marsh pennywort.

The site is private land with no public access.