Rock Springs is a city in Sweetwater County, Wyoming, United States. The population was 23,526 at the 2020 census, making it the fifth most populous city in the state of Wyoming, and the most populous city in Sweetwater County. Rock Springs is the principal city of the Rock Springs micropolitan statistical area, which has a population of 37,975. Rock Springs is known as the Home of 56 Nationalities because of the influx of immigrants from all over the world who came to work in the coal mines that supplied the fuel to power the steam engines of the Union Pacific Railroad. The city's rich cultural heritage is celebrated each summer on International Day, a festival where the foods, costumes, and traditions of residents' ancestors are recreated and enjoyed at Bunning Park in downtown Rock Springs.

Sweetwater County is a county in southwestern Wyoming, United States. As of the 2020 United States Census, the population was 42,272, making it the fourth-most populous county in Wyoming. Its county seat is Green River. By area, it is the largest county in Wyoming. Its southern boundary line abuts the north lines of the states of Colorado and Utah.