Tongchang County is a kun, or county, located in the northeastern region of the far western North Pyŏngan province in North Korea.
The county shares borders with several neighboring districts: Pyŏktong and Chagang's Usi county to the north; Unsan and Songwŏn to the east; Thaechŏn to the south; and Changsŏng and Taegwan to the west.