Pierre Athanase Marie Plantar (March 18, 1920 – February 3, 2000) was a French draughtsman, best known for being the principal perpetrator of the Priory of Sion hoax, which he developed to manufacture evidence that he was a Merovingian dynast and the "Grand Monarch" prophesied by Nostradamus. This deception later inspired a series of BBC Two documentaries, the 1982 pseudohistory book Holy Blood, Holy Grail and the 2003 novel The Da Vinci Code, among others.