What was the ancient name for Britain?

The ancient name for Britain was Britannia. The name Britannia was first used by the Romans, who conquered Britain in the first century AD. The name is thought to come from the Brythons, a Celtic people who lived in Britain at the time. The Brythons called Britain "Prydain" or "Pritannia". The Romans changed the name to Britannia. The name Britannia was used for Britain until the Middle Ages, when it was replaced by the name England.