Darreh Shahr (Persian: دره شهر) is a city in the Central District of Darreh Shahr County, Ilam province, Iran, serving as capital of both the county and the district. Darreh Shahr is in the southeastern part of the province, in the northern foothills of the Kabir Kuh ranges. According to the 2016 census there are 21,900 residents, making it the second-largest city in the province.