A hagiography (; from Ancient Greek ἅγιος, hagios 'holy', and -γραφία, -graphia 'writing') is a biography of a saint or an ecclesiastical leader, as well as, by extension, an adulatory and idealized biography of a preacher, priest, founder, saint, monk, nun or icon in any of the world's religions. Early Christian hagiographies might consist of a biography or vita, a description of the saint's deeds or miracles (from Latin vita, life, which begins the title of most medieval biographies), an account of the saint's martyrdom (called a passio), or be a combination of these.

Christian hagiographies focus on the lives, and notably the miracles, ascribed to men and women canonized by the Roman Catholic church, the Eastern Orthodox Church, the Oriental Orthodox churches, and the Church of the East. Other religious traditions such as Buddhism, Hinduism, Taoism, Islam, Sikhism and Jainism also create and maintain hagiographical texts (such as the Sikh Janamsakhis) concerning saints, gurus and other individuals believed to be imbued with sacred power.

Hagiographic works, especially those of the Middle Ages, can incorporate a record of institutional and local history, and evidence of popular cults, customs, and traditions.

However, when referring to modern, non-ecclesiastical works, the term hagiography is often used today as a pejorative reference to biographies and histories whose authors are perceived to be uncritical of or reverential toward their subject.