Mount Massive is a fourteener in the Sawatch Range of the U.S. state of Colorado. It is the second highest peak in the Rocky Mountains, edging out the third highest, Mount Harvard, by 7 feet (2.1 m), and falling short of Mount Elbert by 12 feet (3.7 m). It is the third highest peak in the contiguous United States (Mount Whitney is the highest peak in the contiguous United States). It is located in Lake County, approximately 10 miles (16 km) west-southwest of Leadville and 18 miles (29 km) east of Aspen. It lies in the Mount Massive Wilderness, part of the San Isabel National Forest.
Mount Massive was first surveyed and climbed in 1873 during the Hayden Survey of the American West; survey member Henry Gannett is credited with the first ascent. Its name comes from its elongated shape: it has five summits, all above 14,000 ft (4,300 m), and a summit ridge over 3 mi (4.8 km) long, resulting in more area above 14,000 ft (4,300 m) than any other mountain in the 48 contiguous states, narrowly edging Mount Rainier in that category. Mount Elbert (14,440 ft (4,400 m) is Mount Massive's nearest neighbor among the fourteeners; it lies about 5 mi (8.0 km) south-southeast of the peak.
A class 2 hiking path leads to the peak from the eastern face. The path is 13.6 mi (21.9 km) round trip, with a 4,500 ft (1,400 m) elevation gain. Among the mountain's fauna are the American pika, the mountain goat, elk, gray jay, martin, and the yellow-bellied marmot.
Prominence: 1,960 ft (597 m)
Peak elevation: 14,428 ft (4,398 m)