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| Posthumous[note 1] | |||||||
| King of Joseon (1392–1897) |
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| Emperor of Korea (1897–1910) | |||||||
| Crown Prince[note 2] | |||||||
| Daewongun[note 3] | |||||||
| Rival king |
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| King Yi[note 4] (1910–1947) |
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| Director of the Royal Family Association (1957–) |
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| Pretenders |
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| Yi Jachun 이자춘 李子春 | |||||||||
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| King of Joseon (posthumously) | |||||||||
| Darugachi | |||||||||
| Reign | 1343–1356 | ||||||||
| Born | 20 January 1315 Aldongcheon Lake, Dongbuk-myeon, Goryeo (now Gyeongheung-gun, North Hamgyeong Province) | ||||||||
| Died | 3 June 1361 (aged 46) Gwiju-dong, Hamheung-bu, Dongbuk-myeon, Goryeo (now Yeongheung-gun, Hamgyeongnam-do) | ||||||||
| Burial | |||||||||
| Spouse | Lady Yi Queen Uihye | ||||||||
| Issue | 5 sons and 2 daughters | ||||||||
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| House | House of Yi | ||||||||
| Father | Yi Chun | ||||||||
| Mother | Lady, of the Munju Bak clan | ||||||||
Yi Ja-chun (Korean: 이자춘; Hanja: 李子春; 20 January 1315 – 3 June 1361) or known by his Mongolian name Ulus Bukha (Korean: 울루스부카; Hanja: 吾魯思不花), was a minor military officer of the Yuan Empire who later transferred his allegiance to Goryeo and became the father of Yi Seonggye, founder of the Joseon Dynasty.
Yi Ja-chun was a mingghan (chief of one thousand) of the Yuan Dynasty in Ssangseong Prefectures (雙城; present-day Kŭmya County, South Hamgyŏng Province, North Korea - territory which was then administered by the Mongol Empire as part of the terms of the vassaldom of Goryeo to the empire). After Ssangseong was annexed by Goryeo under King Gongmin, he migrated to Hamju and got promoted to manho (the equivalent of the Mongolian 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 Seong-gye. He died in Hamgyong in 1361.
Since he was glamorized by his descendants, descriptions of Yi Ja-chun'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 Ja-chun as if for scholar-officials, implying that Yi Ja-chun was not a scholar-official.[citation needed]