Hassan-i Sabbāh (Persian: حسن صباح Hasan-e Sabbāh) or Hassan al-Sabbāh (Arabic: حسن الصباح Ḥasan aṣ-Ṣabbāḥ) (1050s-1124) was a Nizārī Ismā‘īlī missionary who converted a community in the late 11th century in the heart of the Alborz Mountains of northern Persia. He later seized a mountain fortress called Alamut and used it as the headquarters for a decentralized Persian insurrection against the dominant Seljuk Turks. He founded a group of fedayeen whose members are often referred to as the Hashshashin, or "Assassins".