thumb|right|220px|Leatherman Peak, , second highest in Idaho, in the [[Lost River Range in eastern Custer County]]
Custer County is a rural mountain county in the center of the U.S. state of Idaho. As of the 2020 census, the population was 4,275, making it the fifth-least populous county in Idaho. The county seat is Challis. Established in 1881, the county was named for the General Custer Mine, where gold was discovered five years earlier. Custer County relies on ranching, mining, and tourism as its main resources.
Geography
According to the U.S. Census Bureau, the county has a total area of , of which is land and (0.3%) is water. It is the third-largest county in Idaho by area.
The Lost River Range, the state's highest mountains, are located in eastern Custer County. The highest is Borah Peak, the highest natural point in Idaho at . On the western border of the county is Idaho's famous Sawtooth Range; the tallest is Thompson Peak in Custer County, above picturesque Redfish Lake. east are the White Cloud Mountains, the tallest of which is Castle Peak at .
The Salmon River and Big Lost River flow through Custer County.
Adjacent counties
- Lemhi County - north
- Butte County - east
- Blaine County - south
- Elmore County - southwest
- Boise County - southwest
- Valley County - west
Major highways
- 20px US 93
National protected areas
- Challis National Forest (part)
- Sawtooth National Forest (part)
- Sawtooth National Recreation Area (part)
- Hemingway–Boulders Wilderness (part)
- Jim McClure–Jerry Peak Wilderness
- Sawtooth Wilderness (part)
- Cecil D. Andrus–White Clouds Wilderness