Greywell Fen is a 38-hectare (94-acre) biological Site of Special Scientific Interest in Greywell in Hampshire.

[1][2] It is a Nature Conservation Review site, Grade 2,[3] and an area of 13 hectares (32 acres) is a nature reserve called Greywell Moors, which is managed by the Hampshire and Isle of Wight Wildlife Trust.

[4] This 2-kilometre (1.2-mile) long site is calcareous fen.

There is a large area of wet grassland, which is grazed by cattle, and a small area of carr woodland.

Meadow flora include cowslip, dyer's greenweed and pepper-saxifrage.