|• McCune-Reischauer||Onsŏng kun|
|• Revised Romanization||Onseong-gun|
|Province||North Hamgyong Province|
|Administrative divisions||1 ŭp;, 10 workers' districts, 15 ri|
|• Total||430 km2 (170 sq mi)|
|Population (1991 est.)|
Onsŏng County is a county (kun) in North Hamgyong Province, North Korea, located near the border with China. The administrative center is the town (ŭp) of Onsong. Onsong is the alleged site of the former Onsong concentration camp, now closed.
Onsong was one of the six post/garrisons (Chosŏn'gŭl: 육진; Hancha: 六鎭) established under the order of Sejong the Great of Joseon (1418–1450) to safeguard his people from the hostile Chinese and Manchurian nomads living in Manchuria.
Onsong lies along the Tumen River, which forms the border with China. To the north of Onsong is Jilin Province, China. Onsong also contains the northernmost point in Korea, at 43°0'39″ N. Liangshui (Chosŏn'gŭl: 량수진; Hancha: 凉水鎮), in Tumen prefecture, is the closest Chinese town across the river.
The land of Onsong is mainly mountainous, although a part is flatland. It has a continental climate, and is the region of Korea with the longest winter, except the Kaema Plateau. The highest peak is Yŏndubong.
Being mountainous in nature, Onsong is not well suited to agriculture. Ironically, however, it has the highest ratio of rice paddies to dry fields of any district in North Hamgyong Province. Logging is prevalent in the Tumen River basin. Lignite coal is also produced.
Onsong is served by roads and railroads. In winter, it is also possible to cross the frozen Tumen River into China.
Onsŏng County is divided into 1 town ("Ŭp"), 10 worker's districts ("Rodongjagu") and 15 villages ("Ri"):
- Yang Dae-su (Chosŏn'gŭl: 양대수; Hancha: 楊大樹)
- Shin Rip (Chosŏn'gŭl: 신립; Hancha: 申砬), the prefect of Onsong (Chosŏn'gŭl: 온성부사; Hancha: 穩城府使), before the Imjin War
- Jung You-ji (Chosŏn'gŭl: 정유지; Hancha: 鄭有智)
- Choi Gwan (Chosŏn'gŭl: 최관; Hancha: 崔寬)
- Go Gyung-jin (Chosŏn'gŭl: 고경진; Hancha: 高景軫)
- Hyok Kang, the author of the autobiographical This is Paradise!: My North Korean Childhood
- Location of the four forts and the six posts
- Map of Onsong
- (in Korean) In Korean language online encyclopedias: