Buyantu Khan (Mongolian: Буянт Хаан; Mongolian script: ᠪᠣᠶᠠᠨᠲᠦ; Chinese: 普顏篤汗), born Ayurbarwada (Mongolian: Аюурбарбад ᠠᠶᠤᠷᠪᠠᠷᠪᠠᠳᠠ; Chinese: 愛育黎拔力八達), also known by his temple name as the Emperor Renzong of Yuan (Chinese: 元仁宗, April 9, 1285 – March 1, 1320), was the fourth emperor of the Yuan dynasty of China. In addition to being the Emperor of China, he is regarded as the eighth Great Khan of the Mongol Empire, although it was only nominal due to the division of the empire. His regnal name "Buyantu Khan" means "blessed/good Khan" in the Mongolian language. His personal name "Ayurbarwada" was derived from a Sanskrit compound Āyurpārvata (आयुर्पार्वत), which means "the mountain of longevity", in contrast with Emperor Wuzong's name Qaišan (海山, "mountains and seas" in Chinese).

Ayurbarwada was the first Yuan emperor who actively supported the adoption of Confucian principles into the administration system. The emperor, who was mentored by the Confucian academic Li Meng, succeeded peacefully to the throne and reversed his older brother Khayisan's policies. More importantly, Ayurbarwada reinstituted the civil service examination system for the Yuan dynasty.

Ayurbarwada was the second son of Darmabala and Dagi (Targi) of the Khunggirat, and a great-grandson of Kublai Khan (r. 1260–1294). He had been tutored by the Confucian scholar Li Meng, who strongly affected his future political attitudes from his early teens.

In 1305 Bulugan Khatun removed Ayurbarwada from the court and sent him to Honan as the prince of Huai-ning. However, his uncle Temür Khan died without an heir on February 2, 1307, because his son Deshou had died a year earlier before him.

Temür's widow Bulugan of the Bayaud tribe had kept away the Khunggirad-mothered brothers of Khayishan and Ayurbarwada and attempted to set up her favorite, the Muslim Ananda, their uncle and the governor of Ningxia. The Darkhan Harghasun, the right chancellor (Chinese: 右丞相) of the government who became aware of Bulugan's plan, recalled Ayurbarwada and Li Meng from Huaizhou (Chinese: 懷州) to the capital Dadu. They successfully developed a strategy to imprison both Ananda and Bulugan. Afterwards, Ayurbarwada welcomed his older brother Khayishan, who was still far away from Dadu, to succeed to the throne. After the latter's coronation, Ayurbarwada was appointed the Crown Prince in June 1307. The brothers promised each other that their descendants would rule in succession.

Ayurbarwada was made head of the top central administrative organs known as the Zhongshu Sheng under his brother and predecessor Khayishan Külüg Khan. He had surrounded himself with the Chinese scholars Chen Hao, Wang I, Wang Yueh, Zhao Mengfu, Wang Chieh, Chan Yaoho, Shang-ye, Yao sui, and Hsia ku; the artists Shang cheng and Wang Cheng-peng; Chagaan, a scholar from Balkh and Haiya, the Uyghur lyricist.

He was able to read and write Chinese and appreciate Chinese paintings and calligraphy in addition to his deep knowledge of Confucianism and Chinese history. Strongly influenced by Confucian political ethics, he was naturally opposed to his brother's exploitative policies. Khayishan's partisans had accused Li Meng of having advised Ayurbarwada to keep the throne for himself; Li Meng left the court immediately after Khayishan's accession. Ayurbarwada spoke out in Li Meng's defence but accomplished nothing much in the end. His disagreement with his brother's high officials remained concealed until his own enthronement.

Khayishan died in January 1311. Unlike the succession struggle over Yuan throne in 1307, Ayurbarwada's succession to his elder brother Khayishan's throne in April 1311 was a peaceful and smooth transition of the Yuan imperial history. This was made possible by the fact that he was designated by Khayishan as the heir apparent in June 1307, in accordance with their earlier agreement, and had subsequently appointed him as the titular head of the Zhongshu Sheng, similar to Kublai Khan had done when grooming Zhenjin to be his successor. He was saluted under the title of Buyantu in his accession kurultai.