Usi County is a kun, or county, in westernmost Chagang Province, North Korea. It looks across the Yalu River into the People's Republic of China. Within North Korea, it borders Chosan and Kopung to the east, Songwon to the south, and North Pyongan Province's Pyoktong county to the west. Originally part of Pyoktong, it was made a separate county in 1952 as part of a general reorganization of local government; in 1954, it was transferred from North Pyongan to Chagang.

Usi County 우시군
County
Korean transcription(s)
• Hanja	雩時郡
• McCune–Reischauer	Usi-gun
• Revised Romanization	Usi-gun
Map of Changang showing the location of Usi
Country	North Korea
Province	Chagang Province
Administrative divisions	1 ŭp, 1 workers' district, 22 ri
Area
• Total	665 km2 (257 sq mi)
Population  (2008 census)
• Total	42,919
• Density	65/km2 (170/sq mi)

There are no railroads in Usi, but it is connected by road to the neighboring districts of Chosan and Pyoktong, and beyond Pyoktong to Sinuiju. In addition, the Yalu is used for transportation. The stretch of the Yalu in Usi is part of the massive "Lake Supung", North Korea's largest reservoir.

The Yalu valley is farmed for rice, while the upland regions produce maize, potatoes, and sesame. There is little manufacturing. The county's Kaha-ri district is known for its medicinal waters.