Late Goryeo civil official and Neo-Confucian scholar; one of the "Three Recluses" (Sam-eun); art name Poeun (圃隱)

| Life | 1337 ~ 1392 |
| Era | 고려 |
| Clan | 연일 정씨 |
Of the Yeonil Jeong clan (Yeongil Jeong clan), his art name was Poeun (圃隱). A leading Neo-Confucian scholar of late Goryeo, he served as Daesaseong of the National Academy, rose to Chancellor (Sumunha Sijung), and was active in diplomacy with Ming China and Japan.
Deeply learned in Neo-Confucianism, he was called the "progenitor of Eastern principle-learning (ihak, 理學)." He established relief granaries to aid the poor and worked to reform the ritual and legal systems according to the Family Rites of Zhu Xi. His literary collection Poeun Jip (圃隱集) survives.
Keeping his loyalty to the Goryeo dynasty, he opposed Yi Seong-gye's founding of Joseon and was assassinated by Yi Bang-won's men at Seonjukgyo Bridge in Gaeseong in 1392. His integrity is widely known through the sijo poem "Dansimga" (Song of a Loyal Heart).
Neungwon-ri, Mohyeon-eup, Cheoin-gu, Yongin-si, Gyeonggi-do
He had descendants including his son Jeong Jong-seong (鄭宗誠, 1374-1442), and the line continued as the Yeonil Jeong clan.