John Stuart Mill's book Utilitarianism is a classic exposition and defence of utilitarianism in ethics. 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. Mill's aim in the book is to explain what utilitarianism is, to show why it is the best theory of ethics, and to defend it against a wide range of criticisms and misunderstandings. Though heavily criticized both in Mill's lifetime and in the years since, Utilitarianism did a great deal to popularize utilitarian ethics and was "the most influential philosophical articulation of a liberal humanistic morality that was produced in the nineteenth century."

John Stuart Mill (20 May 1806 8 May 1873) was an English philosopher, political economist and civil servant. One of the most influential thinkers in the history of liberalism, he contributed widely to social theory, political theory and political economy. Dubbed "the most influential English-speaking philosopher of the nineteenth century", Mill's conception of liberty justified the freedom of the individual in opposition to unlimited state and social control.Mill was a proponent of utilitarianism, an ethical theory developed by his predecessor Jeremy Bentham. He contributed to the investigation of scientific methodology, though his knowledge of the topic was based on the writings of others, notably William Whewell, John Herschel and Auguste Comte, and research carried out for Mill by Alexander Bain. Mill engaged in written debate with Whewell.A member of the Liberal Party, he was also the first Member of Parliament to call for women's suffrage.