Miniature horses are found all over the world and come in various colours and coat patterns. The designation of miniature horse is determined by the height of the animal, which, depending on the particular registry involved, is usually less than 34-38 inches (82-91 cm) as measured at the withers. While miniature horses are the size of a very small pony, many retain horse characteristics and are considered "horses" by their respective registries.

Miniature horses are friendly and interact well with people. For this reason they are often kept as family pets, though they still retain natural horse behavior and must be treated like an equine, even if they primarily serve as a companion animal. They are also trained as service animals, akin to guide dogs or assistance dogs for people with disabilities.

In the 17th century, miniature horses were bred as pets for Europe's Hapsburg nobility. Records from the court of the French King Louis XIV, circa 1650, note the presence of tiny horses among the exotic creatures in the king's zoo. Paintings and articles featured the miniature horse by 1765. In England, Lady Estella Hope and her sisters carried on a breeding program from original English lines into the mid-nineteen hundreds. However, not all early miniatures were pampered pets of kings and queens. Some were used to work in the English Midlands, Wales and Northern European coal mines as pit ponies.

In the United States, the miniature horse breed was refined during the 20th century. Miniature horses in the USA added additional lines from sources that included the Hackney Pony and the Pony of the Americas.

The Falabella miniature horse was originally developed in Argentina in 1868 by Patrick Newell. When Newell died, the herd and breeding methods were passed to Newell's son-in-law, Juan Falabella. Juan added additional bloodlines including the Welsh Pony, Shetland pony, and small Thoroughbreds. With considerable inbreeding he was able to gain consistently small size within the herd.

South Africa's Miniature Horses were developed in that nation and are known as the South African Miniature Horses, a recognized breed in its own right. Mr. Wynand de Wet of Lindley, South Africa, started in 1945 with two Shetland mares and a stallion. Through strict selection, their offspring became smaller and in 1991 Mr. de Wet bred a mare that was only 66cm tall.

There is an ongoing debate over whether a miniature horse should possess horse or pony characteristics. This is a common controversy within the miniature horse world and also is a hot debate between mini aficionados and other horse and pony breed owners. While technically any member of equus caballus under 14.2 hands is termed a "pony," many breeds, including some miniature breeds, actually retain a horse phenotype and their breed registry therefore classifies them as horses.

Some miniature horse breed standards prefer pony characteristics such as short, stout legs and elongated torsos, while others prefer ordinary horse proportions. Even the name is in dispute, terms such as "Midget Pony" and "Pygmy Horse" used in addition to "Miniature horse" and breed-specific names such as Falabella. The level of controversy is reflected by the presence of over 30 different registries for miniaturized horses or ponies just within the English-speaking world.