Mount Massive is the second-highest summit of the Rocky Mountains of North America and the U.S. state of Colorado. The prominent 14,428-foot (4,398 m) fourteener of the Sawatch Range is located in the Mount Massive Wilderness of San Isabel National Forest, 10.6 miles (17.1 km) west-southwest of the City of Leadville in Lake County, Colorado, United States. Mount Massive edges out the third-highest summit of the Rockies, Mount Harvard, by 7 feet (2.1 m), but falls short of Mount Elbert by 12 feet (3.7 m). It ranks as the third-highest peak in the contiguous United States after Mount Whitney and Mount Elbert.

In the mountaineering parlance of the Western United States, a fourteener is a mountain peak with an elevation of at least 14,000 ft (4267 m). The 96 fourteeners in the United States are all west of the Mississippi River. Colorado has the most (53) of any single state; Alaska is second with 29. Many peak baggers try to climb all fourteeners in the contiguous United States, one particular state, or another region.