Histoire secrète d'Isabelle de Bavière, reine de France is an unpublished medieval-set 1813 historical novel by the Marquis de Sade. Its inception is recounted in a note at the end of the manuscript. In July 1764 Sade set out from Paris for Dijon, to see documents from the time of Charles VI of France at the Carthusian convent (including the Duke of Burgundy's will and the confession of Boisbourdon, Isabelle's favourite), which he alleges were destroyed later at the time of the French Revolution. Its central character is Isabelle herself – beautiful, evil and cruel, with similarities to Juliette and possibly acting as a prototype for Sade's later, most perverted characters.