Warmbloods are a group of middle-weight horse types and breeds primarily originating in Europe and registered with organizations that are characterized by open studbook policy, studbook selection, and the aim of breeding for equestrian sport. The term distinguishes these horses from both heavy draft horses and refined light saddle horses such as the Thoroughbred, Arabian, and Akhal-Teke. Although modern warmbloods are descended from heavier agricultural types systematically upgraded by hotblood influence, the term does not imply that warmbloods are direct crosses of "cold" and "hot".

Studbook selection is a process used in certain breeds of horses to select breeding stock. It allows a breed registry to direct the evolution of the breed towards the ideal by eliminating unhealthy or undesirable animals from the population. The removal of individuals from a population is called culling, and does not suggest killing the animal in question. Typically, culls are castrated or they and their offspring are unable to be registered.