The Rocky Mountain elk (Cervus canadensis nelsoni) is a subspecies of elk found in the Rocky Mountains and adjacent ranges of Western North America.

The Rocky Mountain Elks are the second largest animals in the elk subfamily, behind the Roosevelt elk native to the Pacific Northwest. From there the elk ranges from 500-750 pounds, depending on male or female. Male's length is about 2.4 meters (8 feet) and the females length is 2 meters (6.5 feet). Male's height is about 1.5 meters (5 feet) and females is about 1.3 meters (4.5 feet). They tend to be larger in size and have a brown coloration. The coloration of the Rocky Mountain elk is due to their lighter colored rumps, referred to as "white rumps". These "white rumps" were named by the Shawnee granting the name "Wapiti" to the elks. During the summer, the elk develop a lights more auburn colored coat. Overall, the Rocky Mountain elk displays a dark head color paired with a lighter body color.

The winter ranges are most common in open forests and floodplain marshes in the lower elevations. In the summer they migrate to the subalpine forests and alpine basins. Elk have a diverse habitat range, but are most often found in forest and forest edge habitat and in mountain regions they often stay in higher elevations during warmer months and migrate down lower in the winter. They may even come down the mountain and leave the forest into some grassland for part of the day but head back into the timber in the evening.

Climate change/warming can keep elk in their higher elevation habitats for longer into the winter than normal. Climate changes such as warming have in some cases even increased the seasonal range of elk in the winter. For example, in Yellowstone the climate warming has kept the snow at a lower level than in the past and has given the elk the ability to populate higher ranges than before. The lack of snow in Yellowstone has also given the elk an advantage over the wolves in their predator prey relationship because wolves rely on deep snow to hunt elk in winter ranges of Yellowstone. The total wild population is about one million individuals.

The Rocky Mountain Elk are herbivores that change their diets based on the season. During the winter season, 84% of their diets depended on grasses and shrubs. Based on the shrubs and grasses elk ate 65% of grasses, 15% shrubbery, 5% mosses and lichens, and 2% forbs.

Calfs to cows ratios have been steadily declining by 80% every year. The decline has resulted from human activities that affected the lives of the rocky mountain elk. Older Rocky Mountain elk help produce more successful offspring and females carry offspring for shorter timespans. Males who are older help females conceive earlier than females mating with younger males. Comparably conception of offspring is one week earlier. Nutrition of females affects the success of the offspring.

It has been shown that human hunting of elk has affected their reproductive success. The hunting of elk increased behavioral changes in females causing the elk to lose valuable resources needed. The hunting of elk also affects their patterns during the day. During the day when elk would normally be foraging for food, during hunting season elk will intentionally avoid foraging and avoids any type of roads or trails that hunters may follow. The change of foraging and lack of resources lead to malnutrition and loss of body fat.

The Rocky Mountain elk was reintroduced in 1913 to Colorado from Wyoming after the near extinction of the regional herds. While overhunting is a significant contributing factor, the elk's near extinction is mainly attributed to human encroachment and destruction of their natural habitats and migratory corridors. A year later, twenty-one elk from Jackson Hole, Wyoming were reintroduced to South Dakota's Wind Cave National Park for population increase. Conservation efforts also brought the elk populations in New Mexico from near-zero numbers in the late 1800s and early 1900s, to healthy populations in the 1930s in Northern New Mexico.