Bald Mountain (9150 feet, 2789 m) is a mountain in the western United States in south central Idaho, adjacent to the city of Ketchum in Blaine County. The mountain has one of the higher summits of the Smoky Mountains of Idaho, located in the Sawtooth National Forest. The forested Smoky Mountains were named for their propensity for summer forest fires.

It is the primary ski mountain of the Sun Valley ski resort, and renowned for its lengthy runs at a uniform gradient, at varying levels of difficulty, and with little wind.

In the Sun Valley's fourth year of operation (1939–40), Bald Mountain was opened for lift-served skiing, with a series of three (single-seat) chairlifts, unloading at an elevation of 9,020 feet (2,749 m).

With a base elevation of 5,750 feet (1,750 m) along the Big Wood River at River Run, Baldy's vertical drop is 3,400 feet (1,036 m) along its northeast face. It is served by fourteen ski lifts (an eight-person gondola, a high speed six pack, seven high speed quads, two triple chairlifts, and a surface); Baldy has more uphill capacity per skier than any other ski area. It has 75 runs with 2,054 acres (8.31 km) of on-piste skiing, 645 acres (2.61 km) of which have snowmaking.

The slope ratings are 36% easiest, 42% more difficult, and 22% most difficult. These ratings are relative, not absolute; much of the "easiest" terrain on Bald Mountain would be rated as "intermediate" at most ski areas, as the beginner areas are on the gentler and smaller Dollar Mountain.

Sun Valley's Bald Mountain is independent of the Bald Mountain Ski Area, a modest ski hill near Pierce in Clearwater County in north central Idaho.

Easiest (Green Circle Runs)

• Lower River Run
• Lower College
• Olympic Ridge
• Olympic Lane
• 42nd Street
• Upper College
• Broadway
• Broadway Face
• Lilly Marlane
• Maiden Lane
• Mid Warm Springs
• Lower Warm Springs
• Lower Greyhawk
• Sunset Strip
• Roundhouse Slope
• Roundhouse Lane

More Difficult (Blue Square Runs)

• Mid River Run
• Flying Squirrel
• Upper Canyon
• Blue Grouse
• Cutoff
• Christmas Lane
• Wolverton
• Christmas Ridge
• Upper Janss Pass
• Upper French Dip
• Upper Can-Can
• Graduate
• Lower Cozy
• Lower Limelight
• Warm Springs Face
• Upper Warm Springs
• Race Arena
• Mid Hemingway
• Mid Greyhawk
• Mid Cozy
• Lower Picabo's Street
• Lower Hemingway
• I-80
• Brick's Island
• Upper Canyon
• Mid River Run
• Lower Canyon
• Lower Blue Grouse

Most Difficult (Black Diamond Runs)

• Sleeping Bear
• Exhibition
• Inhibition
• Olympic (Not to be confused with Olympic Lane or Olympic Ridge)
• Fire Trail
• Mayday Bowl
• Lookout Bowl
• Easter Bowl
• Little Easter Bowl
• Rock Garden
• Upper Limelight
• Upper Hemingway
• Upper Picabo's Street
• Upper Greyhawk
• Upper Cozy
• Mid Picabo's Street
• Mid Limelight
• International
• Arnold's Run
• Upper River Run
• Upper Holiday
• Mid Holiday
• Lower Holiday

In the NBC miniseries, 10.5: Apocalypse, this mountain is an extinct volcano that erupts with devastating force. An avalanche of hot gases and ash cascaded down the mountain and buried everything, including the mountain's ski areas, and the towns of Sun Valley, Ketchum, and Hailey. Multiple rescue teams arrived at the scene and dug through the debris caused by Bald Mountain's eruption, looking for any survivors.

• Sun Valley.com - Bald Mountain - ski report
• Idaho Summits.com - photo of Bald Mountain from Proctor Mountain
• Ski Lifts.org – photos of Sun Valley's lifts
• Ski Map.org – vintage maps – Sun Valley (Bald Mtn)