Prince Jeongyang (Korean: 정양군; Hanja: 定陽君; d. 23 March 1397[a]), personal name Wang U (왕우; 王瑀) was the only full older brother of King Gongyang[2] and nobleman in the early Joseon dynasty since his two daughters married both of King Taejo's son and grandson.
[3] Then, after his brother's ascension to the throne, he was promoted into Panmunhaseongsa (판문하성사; 判門下省事), Yeongsansasa (영삼사사; 領三司事) and Jongbusisa (종부시사; 宗簿寺事) and in 1391, he became Yeongmunhabusa (영문하부사; 領門下府事).
[4] One year later, Yi Seong-gye established the new Joseon dynasty and King Gongyang's families were exiled, but since U's daughters married both of Yi's son and grandson, so he escaped from the riots while honoured as both of Prince Majeon (마전군; 麻田郡) and Prince Gwi of Ui (귀의군; 歸義君) at Angam Temple (앙암사; 仰庵寺)[5] in Majeon-gun, Gyeonggi Province (now Misan-myeon, Yeoncheon County, Gyeonggi Province) where the Goryeo royal ancestor rites were held by him and his descendants.
In 1394, U became a target for the treason case of the Wang clan which several officials insisted that he and his two sons got exiled or killed.
After U's death in 1397 amid continued impeachment, the King personally sent a tribute and gave him a posthumous name.