Philosophy in the Bedroom" (La Philosophie dans le boudoir) is a libertine novel written by the Marquis de Sade, a French writer known for his controversial and explicit works. The novel was first published in 1795.

The story of "Philosophy in the Bedroom" is set in a bedroom, where a wealthy libertine named Dolmancé instructs Eugénie, a young and innocent girl, in the ways of libertinism. The novel explores themes of sexual freedom, debauchery, and the rejection of societal norms and moral constraints. It is a highly explicit and provocative work that pushes the boundaries of erotic literature.

Marquis de Sade's works, including "Philosophy in the Bedroom, " have been the subject of controversy and debate for their extreme and often shocking content. They are considered important in the history of erotic literature and as a reflection of the libertine and radical thought of the late 18th century.