Etymologically, the term “supererogation” refers to paying more than is due. Philosophically, it relates to the category of actions that lie beyond the call of duty. Historically, the concept was formed in Roman Catholic theology in the times of the Church Fathers but, following the fierce attacks on it by theologians of the Reformation, has almost become out of use. It was revived by J. O. Urmson in his article “On Saints and Heroes” (see Urmson 1958, cited under the Deontic Structure) and since then has played a major role in (nonreligious) ethical theory. Supererogation serves as a significant challenge to major ethical theories: Can utilitarians accept that obligatory action may be suboptimal (and that the very best action possible for an agent may often be supererogatory)? Can deontologists acknowledge the privileged moral value of actions that are not part of one’s duty but rather lie beyond it? Can virtue ethicists relate supererogatory action to a particular character disposition? Adherents to strict versions of these traditional ethical theories typically indeed deny the very possibility of supererogatory action (as did the Lutheran Reformers). Supporters of the idea of supererogation hold that ethical guidance to action has a double-tier structure: what one must do (the obligatory) and what one can only be encouraged to do (the supererogatory), the latter being concerned with nonobligatory yet (often highly) valuable action. Possible justifications of this two-tier structure lie within a wide spectrum of arguments and distinctions: what can or cannot be expected of average moral agents (on the basis of the “ought-implies-can” principle), accepting omissions of optimal action in terms of excuse, the value of leaving some space in moral action to free personal choice to go beyond given norms, basic conditions of social cooperation versus personal expressions of sympathy and solidarity, the moral as distinct from the rational, maximizing in contrast with satisficing, enforceable as against nonenforceable norms, universalizable norms versus self-imposed ideals, and the general gap between duty and (moral) value. The contested category of supererogation is often discussed through typical examples such as heroic actions, self-sacrifice, volunteering, forgiveness and pardon, and gifts and charity, as well as favors. The discussion of these examples exposes the two levels of the debate about the concept of supererogation: the first, which is mostly conceptual (although informed by normative concerns), relates to the issue of whether we need such a concept at all; the second, which is straightforwardly moral, focuses on the disputed demarcation line between the obligatory and the supererogatory.