The Forest of Dean (map) is a geographical, historical and cultural region in the western part of the county of Gloucestershire (map).
The area is characterised by more than 110 square kilometres (42 sq mi) of mixed woodland, one of the surviving ancient woodlands in England. A large area was reserved for royal hunting before 1066, and remained as the second largest crown forest in England, after the New Forest.
The area gives its name to the local government district, Forest of Dean, and a parliamentary constituency, both of which cover wider areas than the historic Forest. The administrative centre of the local authority is Coleford (map), one of the main towns in the historic Forest area, together with Cinderford (map) and Lydney (map).