Utilitarianism is a classic exposition and defense of utilitarianism in ethics. Written by political economist and civil servant John Stuart Mill, the essay first appeared as a series of three articles published in Fraser's Magazine in 1861; the articles were collected and reprinted as a single book in 1863.

The essay provides support for the value of utilitarianism as a moral theory and defends it against a wide range of criticisms and misunderstandings. Though heavily criticized both in Mill's lifetime and in the years since, Utilitarianism has been credited with popularizing utilitarian ethics and is considered the most influential philosophical articulation of a liberal humanistic morality that was produced in the nineteenth century.