This dissertation examines the ethics of Santideva, an Indian Mahayana Buddhist thinker of the seventh century CE, particularly through his work, the Sikṣadsamuccaya (Compendium of Teaching). This study therefore helps redress a significant imbalance in the scholarship on Buddhist ethics, which has up to now focused primarily on the morality of the Theravada Buddhist tradition. The dissertation incorporates both descriptive and metaethical analyses to answer three questions: What is Santideva's moral theory, and how does it compare with other characterizations of Buddhist ethics? Can one moral theory adequately describe Buddhist moral traditions? Through textual analysis and translations, this thesis offers a exegetical account of the moral thought in the Sikṣasamuccaya , beginning with a description of Santideva's understanding of how to become a bodhisattva, the Mahayana spiritual ideal. I provide an analysis of Santideva's understanding of key moral concepts, with a particular focus on virtuous conduct (sila), skillfulness (kusalatva), and merit (puṇya). I then test the assumption that Buddhist moral theory is homogeneous by comparing the results of this study with those of existing secondary literature on Buddhist ethics, and in particular, I respond to Damien Keown's position that Buddhist ethics can be considered a form of Aristotelian virtue ethics. I highlight those features of Santideva's thought that fit the framework of a virtue ethic, and then discuss the implications of those aspects of the tradition that are not well captured by it. In particular, I consider the utilitarian elements in Santideva's morality. In my conclusion, I attempt to resolve these apparently conflicting styles of moral reasoning with the idea that there is a shift over the course of a bodhisattva's career from a straightforward virtue ethic to a kind of utilitarian hybrid of virtue ethics. I conclude the thesis with some reflections on the value of comparative ethics and the effort to develop a comprehensive moral theory to describe Buddhist traditions.