Ali ibn Isa ibn Mahan (fl. 785 – 3 July 811) was a prominent Iranian military leader of the Abbasid Caliphate in the late 8th and early 9th centuries. Ali's father, Isa ibn Mahan, was an early follower and da'i of the Abbasids; he mutinied after the Abbasid Revolution and was executed by Abu Muslim. Ali himself appears first in 779/80. under Caliph al-Mahdi (775–785), as commander of the caliphal guard (ḥaras). He then served as commander of the guard of the heir al-Hadi (r. 785–786), and continued in the post after the latter's accession. Under al-Hadi, he also occupied the posts of secretary of the army department (diwan al-jund), the powerful post of chamberlain (hajib) and director of the treasures. Under Harun al-Rashid (r. 786–809) he continued to serve as commander of the guard unti