Ancient Scotland was settled by various peoples who arrived by a number of routes from southern, central, and northern Europe. When the Romans came to the British Isles in the first century B.C., they found in the Scottish Highlands a Celtic-speaking people whom they called Caledonians (later known as Picts). In the Lowlands and Southern Uplands were Britons, the Celtic people who had settled present England, called Britain after them.

The boundary of Roman Britain was considered to be as far inside Caledonia as the Roman legions could protect themselves against the fierce natives. Under Agricola, the Romans crushed the Caledonian forces at the battle of Mons Graupius in 84 A.D. Two Roman walls were built to protect Britain—Hadrian's Wall, 122?–28, south of the Cheviot Hills, and the Wall of Antoninus, about 142, between the firths of Forth and Clyde.