Öljei Temür Khan, Bunyashir Khan (full name: Bunyashiri, died 1412) was the Mongol khan of the Northern Yuan dynasty based in Mongolia. He was a son of Elbeg Nigülesügchi Khan and younger brother of Gün Temür Khan. He was one of the Borjigin princes, such as Tokhtamysh and Temur Qutlugh, backed by Tamerlane to seize the throne.

Tsagaan Sechen tells that Bunyashiri (Buyanshir) was born in 1379. Twenty years after his birth, his father, Elbeg, was murdered by the Oirats led by Bahamu and Guilichi. In 1402, his older brother, Gün Temür Khan was killed by Örüg Temür Khan Guilichi in the struggle for the crown.

Due to internal struggles of the Mongols, the infant prince, Bunyashiri, fled to Beshbalik where Timur's governor stationed. Timur ordered his governor to receive him kindly. Bunyashiri converted to Islam while he stayed at the court of Timur in Samarkand, thus making Öljei Temür Khan one of the very notable converts to Islam from the house of Kublai Khan.

However, Örüg Temür Khan Guilichi's victory was short lived when he made several grave miscalculations. The first was when he replaced the Mongol Khan with a Tatar Khan, alienating many other Mongol clans that were not Tatar. The second one was that Örüg Temür Khan Guilichi abolished the name "Great Yuan" (the official name of the former Yuan dynasty), because he needed to show friendly and subordinating gestures towards the Ming dynasty so that he could consolidate his power and conquer other Mongol clans. This move was totally unacceptable to most if not all Mongols who wanted to recover their former glory and retake China proper by defeating the Ming Empire, which originally began as rebellions against the Yuan dynasty.

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