Arthur's queen, reputedly the most beautiful woman in Britain, and the lover of Lancelot, Arthur's best knight. She is occasionally a political pawn in the hands of Mordred, other knights, even Arthur himself, and with the help of Lancelot, she escapes a number of predicaments, including kidnapping by Sir Meliagaunt, burning at the stake, and later, marriage with her step-son. In Malory, she flees after Arthur's death to Amesbury, where she becomes a nun, as well as "abbess and ruler, as reason would." After the last battle in which Arthur and many others are killed, Lancelot comes to find her there, and when Guinevere sees him as she walks with the sisters in the cloister, she swoons three times so "that all ladies and gentlewomen had work enough to hold the queen from the earth." After which Guinevere says these words to Lancelot and her women:

Through this same man and me hath all this war be wrought, and the death of the most noblest knights of the world; for through our love that we have loved together is my most noble lord slain. Therefore, sir Lancelot, wit thou well I am set in such a plight to get my soul heal. And yet I trust, through God's grace and through His Passion of His wounds wide, that after my death I may have a sight of the blessed face of Christ Jesu, and on Doomsday to sit on His right side; for as sinful as ever I was, now are saints in heaven. And therefore, sir Lancelot, I require thee and beseech thee heartily, for all the love that ever was betwixt us, that thou never see me no more in the visage. And I command thee,on God's behalf, that thou forsake my company. And to thy kingdom look thou turn again, and keep well thy realm from war and wrack, for as well as I have loved thee heretofore mine heart will not serve now to see thee; for through thee and me is the flower of kings and knights destroyed.

In her guilt and hope for atonement, Guinevere has put aside earthly things and inspires Lancelot to become a monk. Then, in a vision, Lancelot is told that the queen is dead and he travels to Amesbury to bury Queen Guinevere beside Arthur, her husband.