Nicholas III of Saint Omer (died 30 January 1314) was one of the most powerful and influential lords of Frankish Greece. He was hereditary Marshal of the Principality of Achaea, lord of one third of Akova and of one half of Thebes. He also served on three occasions as bailli of the Principality of Achaea (1300–1302, 1304–1307, ca. 1311–14).