Khong Tayiji (Mongolian: ᠬᠤᠩᠲᠠᠶᠢᠵᠢ, хун тайж; simplified Chinese: 浑台吉; traditional Chinese: 渾台吉; pinyin: Húntáijí), also spelled Qong Tayiji, was a title of the Mongols, derived from the Chinese term Huangtaizi (皇太子; "crown prince").
However, Kublai Khan (who founded the Yuan Dynasty) broke this tradition and installed his second son Zhenjin (Chingem) as Crown Prince.
However, Temür was never formally appointed as the Crown Prince and still not the definite successor.
In 1630s the head of the Dzungars was given the title of Baatur Khong Tayiji by the 5th Dalai Lama.
Thereafter the style "Khong Tayiji" was adopted by Dzungar leader Tsewang Dorji Namjal, son of Galdan Tseren.