Donatien Alphonse François, Marquis de Sade (2 June 1740 – 2 December 1814) (French: [maʁki də sad]), was a French aristocrat, revolutionary politician, philosopher, and writer, famous for his libertine sexuality. His works include novels, short stories, plays, dialogues, and political tracts; in his lifetime some were published under his own name, while others appeared anonymously, of which Sade denied being their author. Sade is best known for his erotic works, which combined philosophical discourse with pornography, depicting sexual fantasies with an emphasis on violence, criminality, and blasphemy against Christianity. He was a proponent of extreme freedom, unrestrained by morality, religion, or law. The words sadism and sadist are derived from his name.

Sade was incarcerated in various prisons and an insane asylum for about 32 years of his life: 11 years in Paris (10 of which were spent in the Bastille), a month in the Conciergerie, two years in a fortress, a year in Madelonnettes Convent, three years in Bicêtre Asylum, a year in Sainte-Pélagie Prison, and 12 years in the Charenton Asylum. During the French Revolution, he was an elected delegate to the National Convention. Many of his works were written in prison.