This thesis 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 perfect 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 Chapter 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, these two knights are portrayed in divergent degrees with obviously contrastive narrative context and their repentance takes a different hue as well. 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. Of particular interest is that Chapters I through IV trace the traditional theological view by looking at St. Thomas Aquinas¡¦ concept of sin and repentance. Aquinas¡¦ doctrinal view allows us to analyze Lancelot and Gawain¡¦s sin and repentance within a chivalric as well as theological domain and provides us a better base with which to understand these two concepts. This research strives to bring about a different perspective in evaluating Malory¡¦s knights.