Mongol ruler in Iran who founded the Il-Khanid Dynasty and, as part of a Mongol program of subduing the Islāmic world, seized and sacked Baghdad, the religious and cultural capital of Islām. Some historians consider that he did more than anyone else to destroy medieval Iranian culture.

Hülegü, a grandson of Genghis Khan, was appointed by his brother Mangu (Möngke) Khan, the fourth great khan of the Mongols, to extend Mongol power in Islāmic areas. Hülegü destroyed the fortress of the Assassins (Assassin) (a militant Islāmic sect) in 1256 at Alāmut in north central Iran. He then defeated the caliph's army and captured and executed al-Mustaʿṣim (Mustaʿṣim, al-), the last of the ʿAbbāsid caliphs, and in 1258 he seized and largely destroyed Baghdad. He captured Syria but was decisively defeated by an Egyptian army in 1260. He then returned to Iran, settling in the province of Azerbaijan.