Donatien Alphonse François Sade, comte de (dônäsyăN´ älfôNs´ fräNswä´ kôNt də säd), 1740–1814, French writer and libertine. He is known as the marquis de Sade —the title he held before becoming count on his father's death (1767). Famous for his licentious prose narratives, he also wrote many essays, antireligious pamphlets, and plays. He fought in the Seven Years War, and after his marriage in 1763 he pursued a life of pleasure and was imprisoned for his scandalous conduct. Charged with numerous sexual offenses, he spent a total of 27 years of confinement in such institutions as the Bastille, the dungeon at Vincennes, and Charenton asylum. During this time he wrote such ribald classics as Justine; ou, Les Malheurs de la vertu (1791), La Philosophie dans le boudoir (1793), and Histoire de Juliette; ou, Les Prosperités du vice (6 vol., 1797).

Released for a time during the French Revolution, he succeeded in having some plays produced by the Comédie Française, and during his final confinement at Charenton he directed theatrical performances by the inmates. De Sade brought to light the controversial theory that since both sexual deviation and criminal acts exist in nature, they are therefore natural. This was in violent opposition to the spirit of his times but made him a precursor of modern psychological thought. The sexual aberration in which cruelty is inflicted in order to attain sexual release is termed sadism after him. Generally banned for obscenity, de Sade's works were almost all published in expurgated or unofficial editions. The complete works, edited by Gilbert Lély, appeared in 1966–68 (8 vol.).

See biographies by G. Lély (tr. 1961, repr. 1970), R. Hayman (1978), F. du P. Gray (1998), and N. Schaeffer (1998); essays by S. de Beauvoir (tr. 1953) and L. L. Bongie (1998); studies by G. Gorer (rev. ed. 1953, repr. 1963), N. Gear (1963), A. Le Brun (tr. 1989), and C. V. Michael (1986 and 1989).