Ketchum is a city in Blaine County, Idaho, United States, in the central part of the state.  It is in the Wood River Valley, adjacent to Sun Valley; the two communities share many resources and both sit in the same valley beneath Bald Mountain, with its world-famous skiing. The city also draws tourists from around the world to enjoy its fishing, hiking, trail riding, tennis, shopping, and more. The airport for Ketchum, Friedman Memorial Airport, is approximately 15 miles (24 km) south in Hailey. The elevation of downtown Ketchum is 5,853 feet (1,784 m).

Ketchum was once an isolated mining and ranching town in the wilds of central Idaho. After the development of Sun Valley in 1936, the city became popular with celebrities, including Gary Cooper and Ernest Hemingway. Hemingway loved Ketchum and the surrounding area, fished, hunted and lived in the valley. It was in Ketchum that Ernest Hemingway took his own life; he and his granddaughter, model and actress Margaux Hemingway, are buried in the Ketchum Cemetery. Singer Ben Lee wrote a song dedicated to Ketchum which appears on his album Something to Remember Me By.

Every Labor Day weekend, Ketchum hosts the Wagon Days festival, an old west themed carnival featuring wagon trains, including narrow wagons actually used to carry ore, a parade, and even simulated street gunfights.