Rashīd ad-Dīn (died 1192) was the leader of the Syrian branch of the Assassins (an Ismāʿīlī Shīʿī Muslim sect) at the time of the Third Crusade. He had his headquarters at a fortress in Maşyāf, in northern Syria, and was known to Westerners as the Old Man of the Mountain. Feared for his practice of sending his followers to murder his enemies, he made several attempts on the life of the Ayyūbid leader Saladin, who opposed the Ismāʿīlī Shīʿī sect.