Mordred or Modred (/ˈmoʊdrɛd/; Welsh: Medraut, Medrod, etc.) is a character in the Arthurian legend, known as a notorious traitor who fought King Arthur at the Battle of Camlann, where he was killed and Arthur fatally wounded. Tradition varies on his relationship to Arthur, but he is best known today as Arthur's illegitimate son by his half-sister Morgause, though in many modern adaptations Morgause is merged with the character of Morgan le Fay. In earlier literature, he was considered the legitimate son of Morgause, also known as Anna, with her husband King Lot of Orkney. His brothers or half-brothers are Gawain, Agravain, Gaheris, and Gareth. The name (from either Old Welsh Medraut, Cornish Modred, or Old Breton Modrot) is ultimately derived from Latin Moderātus.
The first surviving mention of Mordred (here called Medraut), occurs in the Annales Cambriae entry for the year 537:
The Annales themselves were completed between 960 and 970, though their authors drew on older material. Mordred was associated with Camlann even at that early date, but as Leslie Alcock points out, this brief entry gives no information as to whether he killed or was killed by Arthur, or even if he was fighting against him; the reader assumes this in the light of later tradition.