Yi Chach'un (; 20 January 1315 â 3 June 1361), also known as Hwanjo, was a minor military officer of the Yuan Empire who later transferred his allegiance to Goryeo and became the father of Yi Sà Ânggye, founder of the Joseon Dynasty. Yi's Mongolian name was Wulusibuhua ().
Yi Chach'un was a chiliarch of a Yuan Dynasty mingghan in Ssangseong Prefecture (present-day Kà Âmya County, South Hamgyà Âng Province, North Korea - former Goryeo territory annexed by Mongol Empire). After Ssangseong was reconquered by Goryeo under King Gongmin, he migrated to Hamju and got promoted to manho (the equivalent of the Mongolian myriarch of a tümen, lit. ten thousand or chief of ten thousand). He married a Goryeo-Korean lady from Anbyeon, who became Queen Uihye, the mother of Yi Sà Ânggye. He died in Hamgyong in 1361.
Since he was glamorized by his descendants, descriptions of Yi Chach'un's life tend to be contradictory to each other. For example, he is said to have risen to the rank of scholar-official. However, when he died, the king at the time expressed condolences for Chach'un as if for scholar-officials, implying that Yi Chach'un was not a scholar-official.