Abu Sa'id Bahadur Khan (June 2, 1305 – December 1, 1335; Persian: ابو سعید بهادر خان), also spelled Abusaid Bahador Khan, Abu Sa'id Behauder (Modern Mongolian: Бу-Саид Баатар хан,[2] Abu sayid Baghatur Khan, [ˈabusæt ˈbaːtər xaːŋ] in modern Mongolian), was the ninth ruler (c. 1316 – 1335) of the Ilkhanate, a division of the Mongol Empire that encompassed the present day countries of Iran, Azerbaijan, Georgia, and Armenia, as well as parts of Iraq, Turkey, Afghanistan, and Pakistan.

[7] This left the emir Chupan as the de facto ruler of Ilkhanate, but the following years were tumultuous for Abu Sa'id's reign.

Golden Horde khan Özbeg invaded Azerbaijan in 1319 in coordination with Chagatayid prince Yasa'ur who had pledged loyalty to Öljaitü earlier but revolted in 1319.

Abu Sa'id was forced to send Amir Husayn Jalayir to face Yasa'ur while he himself marched against Özbeg.

This victory granted young Abu Sa'id the honorific titles of Baghatur (from Mongolian "баатар", meaning "hero, warrior") and al-Sultan al-Adil (the just Sultan).

[8] Chupan subsequently was given hand of Sati Beg, sister of Abu Sa'id on 6 September 1319, thus growing his family's power greatly.

His sons Timurtash, Shaikh Mahmud, Hasan and Demasq Kaja were given governorships of Anatolia, Georgia, Khorasan and Azerbaijan, respectively.

Using this opportunity, on 25 August 1327, Abu Sa'id had one of Chupan's sons, Demasq Kaja, killed, apparently for his activities with one of Öljaitü's former concubines.

But many emirs including Muhammad Beg, uncle of Abu Sa'id deserted him near Ray, taking 30.000 soldiers with them, leaving Chupan no choice but to retreat to Herat.

Narin Taghai (a nephew of Taghachar and grandson of Kitbuqa[9]) who was responsible for Chupan's downfall[3] and Abu Sa'id's uncle Ali Padshah were granted governorates of Khorasan and Baghdad respectively.

In 1334, Abu Sa'id appointed Amir Musaffar Inaq as governor of Shiraz to the resentment of Sharaf al-Din Mahmudshah Inju, founder of Injuid dynasty, who was ruling Fars region for a while since Chupan's death.

On his return to Persia, the great voyager Ibn Battuta was amazed to discover that the realm which had seemed to be so mighty only twenty years before, had dissolved so quickly.

The Ilkhanate lost cohesion after the death of Abu Sa'id, and that of his successor, Arpa Ke'un, becoming a plethora of little kingdoms run by Mongols, Turks, and Persians, and Arabs.