Grangeville is the largest city in and the county seat of Idaho County, Idaho, United States, in the north central part of the state. Its population was 3,141 at the 2010 census, down from 3,228 in 2000.

Idaho County is a county in the U.S. state of Idaho, and the largest by area in the state. As of the 2020 census, the population was 16,541. The county seat is Grangeville. Previous county seats of the area were Florence (1864–68), Washington (1868–75), and Mount Idaho (1875–1902).