Longs Peak (or "Long's Peak", see below) is one of the 54 "fourteeners" in the Rocky Mountains of Colorado. It can be prominently seen from Longmont, Colorado. It is named after Major Stephen Long, who explored the area in the 1820s. It is very popular to climb.

When taken with its neighbor Mount Meeker, they are sometimes referred to as the Twin Peaks. This is not to be confused with another pair of mountains, called the Twin Sisters.

As the only fourteener in Rocky Mountain National Park, the peak has long been of interest to climbers. The easiest route is not difficult, and was probably first used by American Indians collecting eagle feathers, but the first recorded ascent was in 1868 by surveying part of John Wesley Powell. The East Face of the mountain is quite steep, and is surmounted by a gigantic sheer cliff known as "The Diamond" (so-named because of its shape, approximately that of a cut diamond seen from the side and inverted).

The first proposal to climb the Diamond, in 1954, was met with an official closure by the National Park Service, a stance not changed until 1960. The Diamond was first ascended that year, and the route was listed in Fifty Classic Climbs of North America, although today the "Casual Route" (5.10-) is considered a better climb.

As with Pikes Peak, there is officially no apostrophe in the name, although a number of Colorado residents continue to object to this ruling by the Board on Geographic Names.