Guinevere is said to be the daughter of Leodegrance of Cameliard in late medieval romance. She marries Arthur and then has a love affair with Lancelot which causes the downfall of Camelot. The Welsh Triads speak of "Arthur's Three Great Queens," all named Gwenhwyfar (Triad 56) and name Gwenhwyfar as "more faithless" than the three faithless wives of the Island of Britain (Triad 80). One of the earliest Arthurian stories is about the abduction of Guinevere by Meleagant (or Melyagaunce or Melwas). The story is told in The Life of St. Gildas (c. 1130) by Caradoc of Llancarfan and in the Welsh "Dialogue of Melwas and Gwenhwyfar." It is the subject of the earliest known Arthurian sculpture on the archivolt of the Porta della Pescheria on the Modena Cathedral. The story of the abduction is the central action in Chrétien de Troyes' Lancelot and appears in Malory.
Guinevere has been portrayed as everything from a weak and opportunistic traitor to a fatally flawed but noble and virtuous gentlewoman. In Chrétien's Yvain, the Knight of the Lion, she is praised for her intelligence, friendliness, and gentility, while in Marie de France's Lanval (and Thomas Chestre's Middle English version, Sir Launfal), she is a vindictive adulteress, disliked by the protagonist and all well-bred knights. The early chronicles tend to portray her more inauspiciously, while later authors used her good and bad qualities to construct a deeper character.