Devon is a large county in southwestern England. 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 and Celtic Sea. 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 by area and has a population of 1,141,600 making it the 11th largest. The county town is the cathedral city of Exeter. In addition to Devon County Council, the county contains two unitary authorities (independent from Devon County Council's control): the port city of Plymouth and Torbay, a conurbation of seaside resorts. 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 sq mi), the largest open space in southern England. It is the only English county to have two separate coastlines – a north and southern coastline.
The county is home to part of England's only natural UNESCO World Heritage Site, the Dorset and East Devon Coast, known as the Jurassic Coast for its geology and geographical features. It is also home to Braunton Burrows UNESCO Biosphere Reserve, a dune complex in the north of the county. Along with Cornwall, Devon is known as the "Cornubian massif". This geology gives rise to the landscapes of Dartmoor and Exmoor, the latter two being national parks. Devon has seaside resorts and historic towns and cities, rural scenery and a mild climate, accounting for the large tourist sector of its economy.