Unsan County is a kun, or county, in eastern North Pyongan province, North Korea. Within the province, it borders Hyangsan in the east, Kujang and Nyongbyon in the south, and Tongchang and Taechon in the west. In addition, it is bordered by Chagang province to the east (Huichon) and north (Songwon).
The Kuryong River has formed a steep valley and basin in the center of the county, into which various tributaries flow including the Uhyon River, Choyang River, Yonghung River, and Pungsanchon. The year-round average temperature is 8.2 °C, with a January average of -10.2 °C and an August average of 23.8 °C. The climate is fairly wet, with an average annual rainfall of 1400 mm. 73% of the county's area is forested, while only 15.5% is cultivated.
Of Unsan's cultivated land, most (70%) is dry-field, with numerous cattle farms; local crops include maize, soybeans, sweet potatoes, and vegetables as well as rice. Unsan leads the province in the production of sweet potatoes. Fruit is also raised. Gold and silver are mined, and factories produce textiles and ironware.
In Yongho-ri on the slopes of Kubongsan, there are tombs from the Koguryŏ period. A tomb traditionally held to be that of the Kojosŏn ruler Wiman is also located there.
Unsan is served by the Unsan Line railroad, and is also connected to neighboring districts by road.