A myotonic goat, otherwise known as the fainting goat, is a domestic goat whose muscles freeze for roughly 3 seconds when the goat feels panic. Though painless, this generally results in the animal collapsing on its side. The characteristic is caused by a hereditary genetic disorder called myotonia congenita. When startled, younger goats will stiffen and fall over. Older goats learn to spread their legs or lean against something when startled, and often they continue to run about in an awkward, stiff-legged shuffle.

Slightly smaller than standard breeds of the goat, fainting goats are generally 43 to 64 cm (17 to 25 in) tall and can weigh anywhere from 27 to 79 kg (60 to 174 lb). Males, or bucks, as they are often referred to, can be as heavy as 200 pounds. They have large, prominent eyes in high sockets. Their hair can be short or long, with certain individuals producing a great deal of cashmere during colder months. There appears to be no angora strain of the fainting goat. Common coat colors are black and white; however, most possible coat colors are found in this breed.