Arthur of Dalriada
Son of King Aedán mac Gabrain, who ruled Dál Riada (a Scottish kingdom settled by the Irish, c. 500) in the final quarter of the sixth century. His existence is attested in the Life of St. Columbia (c. 700) and other Irish texts. He had several brothers, including Echoid Find and Domingart.
Aedán apparently fought a battle against the Picts at Miatha, in which Arthur was killed. Aedán was known as a prolific campaigner, and it is likely that Arthur participated in a number of battles before his death. He is said to have fallen in a battle against the forces of King Æthelfrith of Bernicia, his death allegedly being foretold by his father by Saint Columba.
Although he lived later than the traditional dates of Arthur, some scholars, including Richard Barber (The Figure of Arthur), argue for Arthur of Dál Riada as the original prototype of King Arthur. According to this theory, Arthur of Dál Riada was the “Arthur” to which Y Gododdin (a poem written in the north for the northern audiences, contemporary to the life of Arthur of Dál Riada) refers; his fame grew in oral legend until he was eventually attached to battles fought before his time, by other warleaders.
A less controversial theory holds that some of Arthur of Dál Riada’s exploits were later conflated with his more famous predecessor’s (after whom, presumably, Arthur of Dál Riada was named).
Sources
Life of St. Columbia | c. 700
The Figure of Arthur | Richard Barber, 1972
Y Gododdin | Aneirin, c. 600