Mahmud Ghazan (5 November 1271 – 11 May 1304) (غازان خان, Ghazan Khan, sometimes archaically spelled as Casanus by the Westerners) was the seventh ruler of the Mongol Empire's Ilkhanate division in modern-day Iran from 1295 to 1304. He was the son of Arghun, grandson of Abaqa Khan and great-grandson of Hulagu Khan, continuing a long line of rulers who were direct descendants of Genghis Khan. Considered the most prominent of the Ilkhans, he is perhaps best known for converting to Islam and meeting Imam Ibn Taymiyya in 1295 when he took the throne, marking a turning point for the dominant religion of the Mongols in Western Asia (Iran, Iraq, Anatolia and Transcaucasia). One of his many principal wives was Kököchin, a Mongol princess (originally betrothed to Ghazan's father Arghun before his death) sent by his great-uncle Kublai Khan.
Military conflicts during Ghazan's reign included war with the Egyptian Mamluks for control of Syria, and battles with the Turko-Mongol Chagatai Khanate. Ghazan also pursued diplomatic contacts with Europe, continuing his predecessors' unsuccessful attempts at forming a Franco-Mongol alliance. A man of high culture, Ghazan spoke multiple languages, had many hobbies, and reformed many elements of the Ilkhanate, especially in the matter of standardizing currency and fiscal policy.
Ghazan's parents were Arghun and his concubine Kultak Egechi of the Dörben tribe. At the time of their marriage, Arghun was 12. Kultak's elder sister Ashlun was the wife of Tübshin, son of Hulagu and previous viceroy in Khorasan. According to Rashid al-Din, the marriage took place in Mazandaran, where Arghun was viceroy. Ghazan was born on 5 November 1271 in Abaskun (near modern Bandar Turkman) though he was raised in the Ordo (nomadic palace-tent) of his grandfather Abaqa's favorite wife, Buluqhan Khatun, who herself was childless. Ghazan and Arghun didn't see each other until Abaqa's attack on Qaraunas in 1279 where they briefly met.
Ghazan was raised a Christian, as was his brother Oljeitu.