Disciple of Yi Hwang, leader of the Southerners, who raised 2,000 volunteer soldiers in the Imjin War; pen name Chuyeon, posthumous title Chung-gang

| Life | 1542 ~ 1593 |
| Era | 조선 중기 |
| Clan | 단양 우씨 |
U Seong-jeon (1542-1593) was a mid-Joseon civil official and volunteer army leader of the Danyang clan, with courtesy name Gyeongseon, pen names Chuyeon and Yeonam, and posthumous title Chung-gang. He began as an Easterner and became leader of the Southerners. His natural father was the magistrate U Eon-gyeom and his adoptive father U Jun-gyeom; he studied under Yi Hwang and was son-in-law of Heo Yeop, brother-in-law of Heo Gyun and husband of the elder sister of the poet Heo Nanseolheon.
He passed the special civil examination in 1568 (Seonjo 1), served as Geomnyeol and Bongyo and became Busuchan, and in 1572 successfully proposed abolishing the Jeonggong Dogam. He lectured on the Book of Documents at the royal lectures, proposed enforcing the local covenants, and in 1573 proposed sending sacrificial offerings for Gi Dae-seung. He served as magistrate of Suwon in 1576, and in 1581, when his circle thrived and he was seen as arguing too much, he was impeached and dismissed. He later served as Jangnyeong, Saongwon Jeong, Eunggyo and Sain. At the 1575 split between Easterners and Westerners he represented the Easterners with Kim Hyo-won and Ryu Seong-ryong, and after the 1591 heir-designation dispute, when the Easterners divided into hardline Northerners and moderate Southerners, he joined the Southerners. One explanation is that he lived at the foot of Namsan, the "south mountain," while Yi San-hae lived to the north.
When the Imjin War began in 1592 he was magistrate of Suwon, raised 2,000 volunteer soldiers in Gyeonggi under the name Chuuigun, and joined Kim Cheon-il at Ganghwa, winning victories in several places. At Haengju in Gyeonggi he is said to have supported the rear of Gwon Yul. He was specially promoted to Daesaseong of the Seonggyungwan and Jijegyo, but kept fighting as a volunteer leader and pursued the retreating Japanese as far as Uiryeong before falling ill, being taken to Bupyeong in Gyeonggi and dying at 51. His works include the Toegye seonsaeng eonhaengnok, Yeokseol, Igiseol and Gyegap illok.
He represented the Easterners at the 1575 party split and joined the Southerners after the 1591 heir-designation dispute, and is said to have faced political difficulty from Northerner attacks.
In 1592 he raised 2,000 volunteers under the name Chuuigun and fought under Kim Cheon-il, and at Haengju he supported the rear of Gwon Yul.
His service was forgotten under Northerner rule, but under King Jeongjo he was posthumously made Minister of Personnel and Grand Academician and given the title Chung-gang.
His tomb lies beside that of his wife of the Yangcheon Heo clan at Sukgok-ri, Maesong-myeon, Hwaseong, Gyeonggi; the Chuyeon U Seong-jeon tomb precinct (including the U Ha-yeong precinct) was designated Gyeonggi-do Cultural Heritage Material No. 121 on 21 April 2003.
His wife was of the Yangcheon Heo clan, a daughter of Heo Yeop.