Blaine County is a county in the U.S. state of Montana. As of the 2020 census, the population was 7,044. Its county seat is Chinook. The county was named for James G. Blaine, former United States Secretary of State. It is on the north line of the state, and thus shares the southern border of Canada opposite Saskatchewan.

Chinook is a city in and the county seat of Blaine County, Montana, United States. The population was 1,185 at the 2020 census. Points of interest are the Bear Paw Battlefield Museum located in the small town's center and the Bear Paw Battlefield, located 20 miles (32 km) south of Chinook.