The peninsula formed part of what the Romans called Armorica. Coutances was the capital of the Unelli, a Gaulish tribe. It got its name "Constantia" in 298 during the reign of Roman emperor Constantius Chlorus. Under the Carolingians it became known as the Cotentin and was controlled by viscounts. For some time these were members of the Saint-Sauveur family. They lived at Saint-Sauveur on the Douve river.