Belle Fourche is a city in and the county seat of Butte County, South Dakota, United States. Its population was 5,617 at the 2020 census. It is near the geographic center of the United States, which moved some 550 miles northwest from the geographic center of the contiguous United States in Lebanon, Kansas with the admission of Alaska and Hawaii in the mid-20th century.

Butte County is a county in the U.S. state of South Dakota. As of the 2020 census, the population was 10,243. Its county seat is Belle Fourche. The county was established in the Dakota Territory on March 2, 1883, and given the descriptive name based on the French word for a hill.