Mule, a domestic work animal that is the hybrid offspring of a jack (male ass) and a mare (female horse). The offspring of a jenny (female ass) and a stallion (male horse) is called a hinny. Hinnies are considered inferior to mules and are rarely bred. Both mules and hinnies are born sterile.

The mule varies in color from tan to red; some are gray or blonde. It resembles the horse in size and in the shape of its neck. Like the ass, it has a large head, long ears, small hoofs, and a tuft of long hair at the end of its tail. Mules range in height from 12 hands to 17 ½ hands. (A hand equals 4 inches [10 cm].) They may weigh from 600 pounds (272 kg) to 1600 pounds (726 kg).

Mules are primarily used as draft animals to pull heavy loads. Most draft mules are the offspring of a jack and a Belgian draft mare. Draft mules combine the strength of the horse with the endurance and sure-footedness of the ass. Mules are unusually resistant to disease and can withstand heat better than horses. Mules are also bred for racing and riding. They can be trained to jump, to help round up cattle, and to perform in rodeos.

Mules have been bred for at least 3,000 years. They originated in Asia Minor. They have been bred in the United States since the late 18th century, chiefly in the South. They were used primarily as draft animals on plantations and in coal mines.