In moral philosophy, deontological ethics or deontology is the normative ethical theory that the morality of an action should be based on whether that action itself is right or wrong under a series of rules and principles, rather than based on the consequences of the action. It is sometimes described as duty-, obligation-, or rule-based ethics. Deontological ethics is commonly contrasted to consequentialism, utilitarianism, virtue ethics, and pragmatic ethics. In this terminology, action is more important than the consequences.

Ethics or moral philosophy is the philosophical study of moral phenomena. It investigates normative questions about what people ought to do or which behavior is morally right. It is usually divided into three major fields: normative ethics, applied ethics, and metaethics.