Roydon Common is a 194.9-hectare biological Site of Special Scientific Interest east of King’s Lynn in Norfolk. It is also a Grade I Nature Conservation Review site, a National Nature Reserve and a Ramsar site. It is part of the Roydon Common and Dersingham Bog Special Area of Conservation and Roydon Common and Grimston Warren nature reserve, which is managed by the Norfolk Wildlife Trust,

The common is described by Natural England as “one of the best examples in Britain of a lowland mixed valley mire”. It has diverse habitats, including wet acid heath, calcareous fen and dry heath on acid sands. There are rare plants, birds and insects, including the black darter dragonfly