The Order of Assassins (Arabic: حَشّاشِین, romanized: Ḥaššāšīyīn; Persian: حشاشين, romanized: Ḥaššāšīn) was a Nizari Isma'ili religious order founded by Hasan-i Sabbah that existed between 1090 and 1275 AD and conducted high-profile assassinations in the Levant during the time of the crusader states.
During that time, the members lived in the mountain castles in Persia and the Levant, and held a strict subterfuge policy throughout the Middle East, posing a substantial strategic threat to Fatimid, Abbasid, and Seljuk authority, and killing several Christian leaders. Over the course of nearly 200 years, they killed hundreds who were considered leading enemies of the Nizari Isma'ili state. The modern term "assassination" is believed to have stemmed from the tactics used by the Assassins.