Devon is a large county in southwestern England. The county is occasionally referred to as Devonshire, although that is an unofficial name, rarely used inside the county itself and often indicating a traditional or historical context. The county shares borders with Cornwall to the west and Dorset and Somerset to the east. Its southern coast abuts the English Channel and its northern coast the Bristol Channel. The name "Devon" derives from the kingdom of Dumnonia, which was home to the tribe of Celtic people who inhabited this area of the southwestern peninsula of Britain at the time of the Roman invasion in AD 43, Dumnonii—possibly meaning 'Deep Valley Dwellers' or 'Worshippers of the god Dumnonos'.
Devon is the fourth largest of the English counties and has a population of 1,141,600. The county town is the cathedral city of Exeter and the county contains two independent unitary authorities: the port city of Plymouth and the Torbay conurbation of seaside resorts, in addition to Devon County Council itself. Plymouth is also the largest city in Devon. Much of the county is rural (including national park) land, with a low population density by British standards. It contains Dartmoor 954 km2 (368 square miles), the largest open space in southern England.