Although canonical Buddhist philosophy does not offer systematic, meta-ethical argumentation in a manner that might be familiar to readers of Western ethical theories, Buddhism has long been deeply concerned with ethical questions, offering detailed articulations of human flourishing, elaborate moral psychologies, taxonomies of virtues, rules for moral conduct, and instructions on spiritual technologies for ethical self-cultivation. The ethical underpinnings of the Buddhist project manifest differently across Buddhist traditions, although teachings such as the Buddha’s diagnosis of the suffering endemic to the human condition and the way to resolve it in the four noble truths, the workings of karma (literally “action” in Sanskrit) and its effects in shaping the world that a being experiences, and the moral-psychological structure of experience together provide a shared set of foundational principles. How these foundational principles are enacted within the ethical teachings and contemplative practices of different Buddhist traditions varies. Among the early Buddhist schools that emerged in the first few centuries after the lifetime of the Buddha, a distinctive ethical focus is its elaboration of the moral psychology of monitoring and purifying unwholesome qualities of feeling and thinking as an essential task on the path of liberation. With the emergence of Mahāyāna (Sanskrit: “Great Vehicle”) Buddhism around the 1st century bce, the ethical lodestone shifts to the cultivation of bodhicitta (Sanskrit: “awakening mind”)—the radically altruistic intention to achieve enlightenment in order to benefit sentient beings—as well as advancing the figure of the bodhisattva (Sanskrit: “awakening being”) as moral exemplar. Vajrayāna (Sanskrit: “Indestructible Vehicle”) Buddhism upholds the basic ethical view of the Mahāyāna while activating them within a contemplative scheme characterized by elaborate tantric rituals, which are said to conduce to a more expeditious realization and are supported by additional sets of ethical commitments. In addition to exegeses of these traditional Buddhist ethical commitments and the practices that support them, much of the scholarship on Buddhist ethics in the 21st century is concerned with constructing systematic interpretations of traditional Buddhist ethics, applying traditional Buddhist ethics to contemporary moral problems, expanding the scope of Buddhist ethical reflection to articulate activist stances on social justice issues, and interpreting the recent secularization of Buddhist practice in evidence-based contemplative science protocols.