The Forest of Dean is a geographical, historical and cultural region in the western part of the county of Gloucestershire, England. It forms a roughly triangular plateau bounded by the River Wye to the west and north-west, Herefordshire to the north, the River Severn to the south, and the City of Gloucester to the east.
The area is characterised by more than 110 square kilometres (42.5 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, the largest being New Forest. Although the name is used loosely to refer to the part of Gloucestershire between the Severn and Wye, the Forest of Dean proper has covered a much smaller area since medieval times. In 1327 it was defined to cover only the royal demesne and parts of parishes within the hundred of St Briavels, and after 1668 comprised the royal demesne only.