Bénigne d'Auvergne de Saint-Mars was a
French prison governor in the late 17th and early 18th century. He is best known as the apparent keeper of the
Man in the Iron Mask. According to letters written by Saint-Mars to various officials and ministers of France, he had in his custody a prisoner of State, whom he carried with him from
Pinerolo to the
Lérins Islands, and later to the
Bastille.