Miles City is a city in and the county seat of Custer County, Montana, United States. The population was 8,354 at the 2020 census.

Custer County is a county located in the U.S. state of Montana. As of the 2020 census, the population was 11,867. Its county seat is Miles City. The county was established on June 2, 1865, as one of the nine original counties of the Territory of Montana named Big Horn County, and was renamed on February 16, 1877, in honor of Lieutenant Colonel George Armstrong Custer.