Ketchum is a city in Blaine County, Idaho, United States. Located in the central part of the state, the population was 3,555 at the 2020 census, up from 2,689 in 2010. Located in the Wood River Valley, Ketchum is adjacent to Sun Valley and the communities share many resources: both sit in the same valley beneath Bald Mountain, with its skiing. The city also draws tourists to its fishing, hiking, trail riding, tennis, shopping, art galleries, and more.