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Roman Britain (Latin: Britannia or, later, Britanniae, "the Britains") refers generally to the period of Roman rule over areas on the island of Great Britain from ad 43 to 409 or 410.[1]:129–131[2]

Julius Caesar invaded Britain in 55 and 54 bc as part of his Gallic Wars.[3][4] The Britons had been overrun or culturally assimilated by the Celtic tribes during the British Iron Age and had been providing aid to Caesar's enemies. He received tribute, installed a friendly king over the Trinovantes, and returned to Gaul. Planned invasions under Augustus were called off in 34, 27, and 25 bc. In ad 40, Caligula assembled 200,000 men at the Channel only to have them gather seashells. Three years later, Claudius directed four legions to invade Britain and restore an exiled king over the Atrebates.[5] The Romans defeated the Catuvellauni but then organized their conquests as the Province of Britain (Latin: Provincia Britannia). By the year 47, the Romans held the lands southeast of the Fosse Way.