On Liberty is a book by John Stuart Mill, one of the most celebrated philosophers on the subject of leadership and governing ideals. The book focuses on Mill's philosophy on utilitarianism which is one of his defining principles. The principles of the book are focused on developing a relationship between the ruling authority and liberty. The work was meant to be a short essay but it was expanded to cover all his principles about liberty and utilitarianism. The work begins like most of his philosophical works; by introducing the historical background about the struggle that has always existed between liberty and authority.

Mill argues that in a way democracy encourages what he terms as "tyranny of the majority". He argues that the authority of the ruling class should be controlled by the liberty and the freedoms of the citizens. With these views he sets the tone for the whole book and goes into great details about the relationship between liberty and authority. Mill stated that this book was not his work alone because he collaborated with his wife Harriet Mill and this is evident especially when compared to his previous essays. The book was well received and it remains a philosophical classic.