Athrwys (also Arthwys) was a 7th century King (or perhaps prince) from Wales. In about AD 645, Athrwys appears to have seized the throne of Ergyng from his uncles, Caradog & Morgan. He ruled there for about ten years before his death.
Some scholars propose Athrwys as a prototype for the legendary King Arthur. Particularly relevant are King Arthur's associations with Caer-Legeion-guar-Uisc (Caerleon) which was said to have been one of his major courts, which lies deep in the heart of King Athrwys' home kingdom. Blackett & Wilson followed by Barber & Pykitt further argue that King Athrwys actually was the King Arthur by pushing his lifetime back to the traditional Arthurian period in the early 6th century.