A horse breed is a selectively bred population of domesticated horses, often with pedigrees recorded in a breed registry. However, the term is sometimes used in a very broad sense to define landrace animals, or naturally selected horses of a common phenotype located within a limited geographic region. Depending on definition, hundreds of "breeds" exist today, developed for many different uses. Horse breeds are loosely divided into three categories based on general temperament: spirited "hot bloods" with speed and endurance; "cold bloods," such as draft horses and some ponies, suitable for slow, heavy work; and "warmbloods," developed from crosses between hot bloods and cold bloods, often focusing on creating breeds for specific riding purposes, particularly in Europe.

Horse breeds are groups of horses with distinctive characteristics that are transmitted consistently to their offspring, such as conformation, color, performance ability, or disposition. These inherited traits are usually the result of a combination of natural crosses and artificial selection methods aimed at producing horses for specific tasks. Certain breeds are known for certain talents. For example, Standardbreds are known for their speed in harness racing. Some breeds have been developed through centuries of crossings with other breeds, while others, such as Tennessee Walking Horses and Morgans, developed from a single sire from which all current breed members descend. There are more than 300 horse breeds in the world today.

This page is a list of horse and pony breeds, and also includes terms for types of horse that are not breeds but are commonly mistaken for breeds. While there is no scientifically accepted definition of the term "breed," a breed is defined generally as having distinct true-breeding characteristics over a number of generations; its members may be called "purebred". In most cases, bloodlines of horse breeds are recorded with a breed registry. However, in horses, the concept is somewhat flexible, as open stud books are created for developing horse breeds that are not yet fully true-breeding. Registries also are considered the authority as to whether a given breed is listed as a "horse" or a "pony". There are also a number of "color breed", sport horse, and gaited horse registries for horses with various phenotypes or other traits, which admit any animal fitting a given set of physical characteristics, even if there is little or no evidence of the trait being a true-breeding characteristic. Other recording entities or specialty organizations may recognize horses from multiple breeds, thus, for the purposes of this article, such animals are classified as a "type" rather than a "breed".