Guinevere has stories about her from medieval Welsh prose.
Guinevere . She is also found in medieval Welsh prose , in the mid-late 12th-century tale Culhwch and Olwen , as Arthur 's wife Gwenhwyfar . This story first appeared in Chrétien de Troyes 's Lancelot , the Knight of the Cart and became a motif in Arthurian literature , starting with the Lancelot-Grail of the early 13th century and carrying through the Post-Vulgate Cycle and Thomas Malory 's Le Morte d'Arthur .