Tolui (also rendered Toluy, c. 1190–1232) was the youngest son of Genghis Khan by Börte. His ulus, or territorial inheritance, at his father's death in 1227 was the homelands in Mongolia, and it was he who served as civil administrator in the time it took to confirm Ögedei as second khan. Before that, he had served with distinction in the campaigns against the Jin and the Khwarezmid Empire.

Perhaps more important is the role his family, the Toluids, had in shaping the destinies of the Mongol Empire. Through his wife Sorghaghtani Beki, Tolui fathered Möngke, Kubilai, Ariq Boke, and Hulagu, and thus was the progenitor of the last of the great Khans, the Yuan Dynasty of China, and of the Il Khans.

Rivalry between the Toluids and the sons of Ögedei and Jöchi caused the stagnation and infighting during the regency periods after the deaths of Ogedei and his son Güyük.

However, it was a rivalry from among Tolui's own sons—that of Kubilai and Arik Boke—that fragmented the power of the empire and set the western khanates against each other in the early 1260s.