Pierre Plantard de Saint-Clair (born Pierre Athanase Marie Plantard, 18 March 1920 β 3 February 2000) was a French draughtsman, best known for being the principal perpetrator of the alleged hoax Priory of Sion, by which he claimed from the 1960s onwards that he was a direct and legitimate male line Merovingian descendant of Dagobert II and the "Great Monarch" prophesied by Nostradamus.
Today in France, he is commonly regarded as a charlatan.