Tümen Jasagtu Khan

Zasagt Khan (; ), born Tümen (; ) (1539–1592), until his death in 1592. He succeeded Darayisung Gödeng Khan and ruled directly over the Chahar. During his reign, the Mongols conquered the Daur and Evenk tribes.

Zasagt Khan was the first of three sons of Darayisung Gödeng Khan. His authority was validated by Altan Khan, and he later coordinated Altan's actions to win over the Uriyangkhai and Daur Mongols. His relatives, Abtai Khan and Khutughtai Sechen Khung Taiji, brought a significant portion of the Four Oirats back into the Mongol fold. In addition to conducting successful raids against the Ming dynasty, Zasagt Khan conquered Koko Nur and appointed his son as its ruler.

In 1576, Zasagt Khan and other Mongol princes adopted Tibetan Buddhism after being converted by Ilduni Sanggiduktshi Garma Lama. He assembled the Six Tumens and initiated legal reforms. He compiled a new code of law reportedly based on the Yekhe Zasag of Genghis Khan, earning him the title Jasagtu ("law-giver"). He made peace with the Right Wing Tumens and conferred official titles upon their leaders. He also compelled three Jurchen tribes in Manchuria, including the Jurjis and the Yekhe Tungusians, to pay tribute.

Zasagt Khan died in 1592.