Mount Washburn, Mountain summit in Yellowstone National Park, US

Mount Washburn is a 10,219-foot (3,115 m) summit in the Washburn Range of Yellowstone National Park, Wyoming. Its broad top is bare gray and brown rock, with snow patches in gullies and slopes of pale green grass and dark green conifers. A two-storey lookout with a flat roof and catwalk stands on the summit, with two dark circular tanks attached to its lower level.

On August 29, 1870, members of the Washburn-Langford-Doane Expedition climbed the peak and named it after their leader, Henry D. Washburn. Lieutenant Gustavus Cheyney Doane wrote the first widely read account of the summit view. By 1879 tourists were already climbing to a tin mustard box on the top that held about fifty autographs.

The summit tower is one of three active fire lookouts in Yellowstone. Its first floor holds a small visitor center and restrooms, the second an observation deck, and the top floor a ranger's residence closed to the public. The peak was named in 1870 for expedition leader Henry D. Washburn.

Two trails reach the summit: from Dunraven Pass, 3 miles (4.8 km) with 1,393 feet (425 m) of gain; from the Chittenden parking area, 2.25 miles (3.62 km) with 1,491 feet (454 m). The summit lookout has a visitor center and restrooms on the first floor and an observation deck on the second; the ranger's residence above is closed. Summer trails are among the park's most frequented.

Mount Washburn is an ancient volcano that collapsed in an eruption from itself or the nearby Yellowstone Caldera. It is one of three active fire lookout towers in Yellowstone, and the summit building has a small visitor center and restrooms on the first floor, an observation deck on the second, and a ranger's residence on the top floor closed to the public.