Yvain (Ywain or Owain) was the son of King Urien. Yvain was known in Welsh legend as Owain.
Most of the early legend, does not give Yvain's mother's name, but some later legends say that Yvain's mother was Morgan le Fay, the half-sister of King Arthur and wife of Urien (such as in the Suite du Merlin (Post-Vulgate) and in Le Morte d'Arthur). According to Vulgate Merlin, Yvain's mother is Brimesent.
According to the Welsh Triads, Urien Rheged was married to the goddess Modron, the daughter of the god Avallach. The legend has it that Modron was the mother of Owain (Yvain). Owain also had a sister, named Morvudd. In the Lady of the Fountain (Mabinogion), his father was Urien, but his mother wasn't mentioned. His grandfather was Kynverchin or Kynvarch, and he was first cousin of Gwalchmei (Gawain).
He was known as Yvain the Valiant or Yvain the Great. There were several characters that were named Yvain. Yvain also had a brother of the same name, but this Yvain was usually known as Yvain the Bastard. In the Vulgate Lancelot, there are other Yvains, including Yvain of Lionel, Yvain of the White Hands, Yvain of Cenel (or of Rivel), and Yvain the Deer.
Yvain was the hero of the same story told by the Welsh, French and English authors. The Welsh title was called the Lady of the Fountain, where the hero was Owain or Owein, the son of Uryen Rhegd (Urien). Chretien de Troyes wrote the French version, called Knight of the Lion or Yvain (c. 1170). While the English version was called Ywain and Gawain (c. 1350).
Yvain killed the knight of the fountain (known as Esclados the Red in Knight of the Lion and as the Black Knight in Mabinogion), but was trapped in his opponent's castle. Lunete (Luned), a companion to the Lady of the Fountain (Laudine?), helped Yvain to escape, as well as helping the hero to woo and marry the countess. See Yvain and the Lady of the Fountain for the full story.
When he attended tournament, he overstayed at King Arthur's court, causing a separation between he and his wife. A separation that caused Yvain to lose his wits, until he was cured of the madness by a lady.
Yvain won a strange companion when he rescued a lion, and killed a dragon. Yvain went on a series of adventure when he helped one lady after another. With the help of the lion, Yvain killed the giant Harpin of the Mountain (Harpin de la Montagne).
One of the women he rescued was Lunete. Lunete had lost favour with the Lady of the Fountain, and the lady's jealous seneschal plotted to have her executed. Yvain defeated the seneschal and his brother through trial by combat.
Lunete, in the end, helped Yvain to reconciled with his wife Laudine. Yvain was said to be the father of Idrus, according to Geoffrey of Monmouth.
According to Geoffrey, Yvain became king of
According to the Vulgate Cycle, Yvain led the first battalion in the battle of Salisbury Plain (Camlann), and killed many Saxons. Yvain rescued Arthur from the King of Northumbria, whom he killed. Yvain helped Arthur to remount, only to be struck down by Mordred.
When Yvain found out about his mother's plot to murder his father, he rescued his sleeping father, before Morgan could strike a blow with her father's sword. Instead of having his mother arrested or killed, Yvain allowed her to escape, provided Morgan never attempt to murder her husband.
When Arthur revealed to the court of his sister's plots against him, he also suspected his nephew (Yvain). Since he could not trust Yvain, Arthur banished him from attending his court. Through Gawain's love for his cousin, he left Arthur's court, and accompanied Yvain in their adventure, where they met Marhaus (Morholt), brother-in-law of the King of Ireland.