The bighorn sheep has tan or brown fur. It has a white belly, rump and muzzle. It is best known for its large horns. The rams or males have large, thick curving horns. The ewe's or female's horns are more slender and less curved. Males weigh between 125-300 pounds, females weigh between 75-200 pounds. The bighorn is a good climber and jumper. Its hooves are hard around the outside and soft on the inside, which help give them traction on slippery rocks.

The bighorn sheep can be found in the Rocky Mountains from southern Canada to Colorado and parts of Nevada, western Texas and eastern California and northern Mexico. The bighorn changes its home range seasonally. In warm months, it grazes on mountain slopes; in colder months it moves down to valleys. Female bighorns live in groups of five to fifteen sheep made up of ewes and their young. Males live in groups of two to five sheep. In the winter bands of ewes may join together and form large groups of up to 100 sheep. Males will join the female groups during mating season.

Bighorn sheep live in alpine meadows, mountain slopes and foothills. They like areas with rocky slopes they can climb to evade predators.

The bighorn sheep browses on grasses, clover and sedges in warm months. In colder months, it eats woody plants like willow and sage. Bighorn sheep in desert areas often eat brushy plants like holly and cactus. When it is not grazing, it will lie down and chew its cud.

In the fall, males have head butting contests to establish dominance. They run at each other at speeds of up to 20 miles an hour and ram their heads together. Rams usually only fight with rams who have horns that are about the same size as their horn. Head butting contests can last as long as 20 hours! The dominant ram will mate with more females than the other rams. When a male is ready to mate, he will go into a herd of females. The female will chase the male before they mate. Sometimes a male will kick a female to get her to chase him. Females have their babies on a cliff that's hard to access. They have one baby. Lambs are woolly and white and have little horns. They can walk and climb by the first day. The lamb will stay hidden where it was born for about a week and then it will start to follow its mother.

It will be weaned when its is about five months old. Male lambs will leave their mother and join a male group when they are between two and four years old. Female lambs will usually remain with their mother's group for her whole life.

Sometimes when a group of bighorn sheep is threatened by a predator like the wolf, they will group together in a circle and face out towards the predator.