In Arthurian legend, Igraine is the mother of King Arthur. She is also known in Latin as Igerna, in Welsh as Eigyr, in French as Igerne, in Thomas Malory's Le Morte d'Arthur as Ygrayne (often modernized as Igraine) and in Wolfram von Eschenbach's Parzival as Arnive. She is the wife of Uther Pendragon, but her first husband was Gorlois; her daughters by him are Elaine, Anna-Morgause, and Morgan le Fay.
Geoffrey of Monmouth
The first surviving mention is in Geoffrey of Monmouth's Historia Regum Britanniae, where she enters the story as the wife of Gorlois, Duke of Cornwall. King Uther Pendragon falls in love with her and attempts to force his attentions on her at his court. She informs her husband who departs with her to Cornwall without asking leave. This sudden departure gives Uther Pendragon an excuse to make war on Gorlois. Gorlois conducts the war from the castle of Dimilioc but places his wife in safety in the castle of Tintagel.Disguised as Gorlois by Merlin, Uther Pendragon
Source:
http://en.wikipedia.org/wiki/Egraine