Crook County is a county in the northeastern corner of the U.S. state of Wyoming. As of the 2020 United States Census, the population was 7,181, making it the third-least populous county in Wyoming. Its county seat and largest city is Sundance. The county is located at the northwestern extreme of the Black Hills, which are its defining geographical feature.

Sundance is a town in and the county seat of Crook County, Wyoming, United States. Its population was 1,032 at the 2020 census. The town is named after the Sun Dance ceremony practiced by several American Indian tribes.