Pierre Louis Jean Casimir de Blacas d'Aulps, 1st Count (comte), then 1st Duke (duc) of Blacas, and later also 1st Prince of Blacas (10 January 1771, Avignon, Vaucluse, France – 17 November 1839, Vienna, Austria) was a French antiquarian, nobleman and diplomat during the Bourbon Restoration.