This monograph aims to analyze the notions of sin and repentance of Lancelot and Gawain in Malory''s Morte Darthur so as to unveil what Malory''s ideal knight is to be like. While the traditional view takes Lancelot as a perfet knight and Gawain a reckless one because of their different dispositions, I approach these two characters from their breach of the chivalric code and their sequential penitence. Chapter I and II will study respectively how Lancelot and Gawain sin in the world of chivalry because of their wrongdoings. Although these two knights have both sinned, yet, in Malory''s hands, they are portrayed in divergent degrees with obviously contrastive narrative context . Chapter III examines the repentance of Lancelot and Gawain and takes note that although both knights repent for their sins, forgiveness is granted to the former exclusively whereas the latter is denied such a treatment. Chapter IV concludes that such difference or prejudice is indicative of Malory''s evaluation of Lancelot and Gawain in accordance with how the two knights handle their misdeeds and this implies the author''s conception of what a perfect knight should be.