Yvain

Sir Ywain (also called Owain, Yvain, Ewain or Uwain) is a Knight of the Round Table and the son of King Urien in Arthurian legend. The historical Owain mab Urien, on whom the literary character is based, was the king of Rheged in Great Britain during the late 6th century. Ywain was one of the earliest characters associated with King Arthur, being mentioned in Geoffrey of Monmouth's Historia Regum Britanniae. He was also one of the most popular, starring in Chrétien de Troyes' Yvain, the Knight of the Lion and appearing prominently in many later accounts.
See more at Wikipedia.org...

The Chrètien de Troyes romance written about 1170, containing the earliest literary example of a tournament .

[Arthurian] The son of Urien, King of Rheged. Yvain appears in the Book of Taliesin and then in The Dream of Rhonabwy, in which he plays a game with Arthur. In Chrétien de Troyes's Yvain (Le Chevalier au Lion) and the Welsh Owein he kills a woman's husband, marries her, loses and eventually regains her love. He also appears in a number of later romances, among which Le Morte d'Arthur, where his is one of the last knights to die (at Mordred's hand) before the death of the King himself.