| Korean name | |
| Hangul | 정구 |
|---|---|
| Hanja | 鄭逑 |
| RR | Jeong Gu |
| MR | Chŏng Ku |
| Art name | |
| Hangul | 한강, 회연야인 |
| Hanja | 寒岡, 檜淵野人 |
| RR | Hangang, Hoeyeonyain |
| MR | Han'gang, Hoeyŏnyain |
| Courtesy name | |
| Hangul | 도가, 가보 |
| Hanja | 道可, 可父 |
| RR | Doga, Gabo |
| MR | Toga, Kabo |
| Posthumous name | |
| Hangul | 문목 |
| Hanja | 文穆 |
| RR | Munmok |
| MR | Munmok |
Chŏng Ku (Korean: 정구; Hanja: 鄭逑; 9 July 1543 – 5 January 1620) was a Korean historian, philosopher, poet, and politician of the Joseon period. He learned from the Korean scholars Yi Hwang from 1563 to 1573 and Cho Sik from 1566 to 1573. A key figure of the Neo-Confucian literati, he established the Yeongnam School and set up the Paengmaewŏn (백매원, 百梅園), a private Confucian academy. His pen names were Hangang (한강; 寒岡) and Hoeyŏnyain (회연야인; 檜淵野人), and courtesy name was Toga (도가; 道可) and Kabo (가보; 可父).
He was the ideological successor of Yi Hwang and Cho Sik, moral support of Namin faction and Bokin faction. His masters were Hŏ Mok, Yun Hyu, and Yun Sŏndo. There was a conflict called the Yesong Controversy (예송논쟁) then polemic of the Namin faction. He came from the Jinju Jeong clan (진주 정씨; 晉州 鄭氏).