Big Horn County is a county in the U.S. state of Wyoming. As of the 2020 United States Census, the population was 11,521. The county seat is Basin. Its north boundary abuts the south boundary of Montana.

Basin is a town in, and the county seat of, Big Horn County, Wyoming, United States. The population was 1,225 at the 2020 census. The community is located near the center of the Bighorn Basin with the Big Horn River east of the town. Basin's post office, built in 1919, is listed on the National Register of Historic Places.