Blaine County is a county in the U.S. state of Idaho. As of the 2020 United States Census, the population was 24,272. The county seat and largest city is Hailey. It is also home to the Sun Valley ski resort, adjacent to Ketchum.

Hailey is a city in and the county seat of Blaine County, in the Wood River Valley of the central part of the U.S. state of Idaho. The population was 7,960 at the 2010 census, up from 6,200 in 2000. Hailey is the site of Friedman Memorial Airport (SUN), the airport for the resort area of Sun Valley/Ketchum, 12 miles (19 km) north. The town of Bellevue is a few miles south. From 1882 to 1895, Hailey was the county seat of now-defunct Alturas County.