Riothamus

Riothamus (also spelled Riutimus or Riotimus) was a Romano-British military leader, who was active circa AD 470. He fought against the Goths in alliance with the declining Roman Empire. He is called "King of the Britons" by the 6th-century historian Jordanes, but the extent of his realm is unclear. Riothamus is a Latinization of the Brythonic personal name *Rigotamos, meaning 'king-most', 'supreme king' or 'highest king'. Though it is still a matter of debate, several scholars consider his life to have been one of the possible sources for the King Arthur legend.

Realm

It is not clear whether Jordanes' "Britons" refers to the Britons of Great Britain itself, or of Armorica, which was undergoing significant British settlement and later came to be known as Brittany. The Bretons retained strong links to Britain, as is reflected in the names Kernow (now Cornwall) and Dumnonia (now Devon) being found as Cornouaille and Domnonée in Armorica. The distinction between insular and continental Britons may not have had very much meaning at the time, as ecclesiastics such as St. Winwaloe were associated with Brittany and Great Britain alike, and King Mark ('Hound of the Sea') apparently ruled Britons/Bretons on both sides of the English Channel.