Mahmud Ghazan (1271–1304) (sometimes referred to as Casanus by Westerners) is the seventh ruler of the Mongol Empire's Ilkhanate division in modern-day Iran from 1295 to 1304.

He is the son of Arghun and Quthluq Khatun, continuing a long line of rulers who are direct descendants of Genghis Khan.

Considered the most prominent of the Ilkhans, he is best known for making a political conversion to Islam in 1295 when he takes the throne, marking a turning point for the dominant religion of Mongols in Central Asia.

His principal wife is Kokechin, a Mongol princess sent by Kublai Khan, and escorted from the Mongol capital to the Ilkhanate by Marco Polo.

Military conflicts during Ghazan's reign include war with the Egyptian Mamluks for control of Syria, and battles with the Turko-Mongol Chagatai Khanate.

Ghazan also pursues diplomatic contacts with Europe, continuing his predecessors' unsuccessful attempts at forming a Franco-Mongol alliance.

A man of high culture, Ghazan speaks multiple languages, has many hobbies, and reforms many elements of the Ilkhanate, especially in the matter of standardizing currency and fiscal policy.