A feral horse is a free-roaming horse of domesticated stock. As such, a feral horse is not a wild animal in the sense of an animal without domesticated ancestors. However, some populations of feral horses are managed as wildlife, and these horses often are popularly called "wild" horses. Feral horses are descended from domestic horses that strayed, escaped, or were deliberately released into the wild and remained to survive and reproduce there. Away from humans, over time, these animals' patterns of behavior revert to behavior more closely resembling that of wild horses. Some horses that live in a feral state but may be occasionally handled or managed by humans, particularly if privately owned, are referred to as "semi-feral".

The Wild and Free-Roaming Horses and Burros Act of 1971 (WFRHBA), is an Act of Congress, signed into law by President Richard M. Nixon on December 18, 1971. The act covered the management, protection and study of "unbranded and unclaimed horses and burros on public lands in the United States."