The term "warmblood" describes a category of sport horse breeds rather than a single breed, encompassing numerous registries that share common breeding philosophies while maintaining distinct identities. The name derives from the historical classification of horses as "hot-blooded" (Arabians, Thoroughbreds), "cold-blooded" (draft breeds), or "warm-blooded" (crosses combining characteristics of both). Modern warmbloods represent sophisticated breeding programs blending these influences.
Major warmblood registries include the Hanoverian, Dutch Warmblood (KWPN), Oldenburg, Holsteiner, Westphalian, Trakehner, Danish Warmblood, Swedish Warmblood, Belgian Warmblood (BWP), Selle Français, and numerous others. Each maintains its own studbook, breeding standards, and selection processes while participating in international sport horse breeding exchanges. The term "sport horse" is often used interchangeably with warmblood in modern contexts.
Registry structures differ from closed-studbook breeds like Thoroughbreds. Most warmblood registries operate as open or semi-open studbooks, accepting approved individuals from other warmblood registries and occasionally incorporating Thoroughbred or other blood to enhance specific qualities. This approach enables genetic exchange that improves sport horse populations while maintaining registry standards through rigorous approval processes.
Breeding philosophy unites warmblood registries more than common ancestry. All aim to produce competitive sport horses through systematic evaluation, selection, and breeding of horses demonstrating athletic ability, correct conformation, quality movement, and suitable temperament. Performance testing, young horse championships, and breeding value indices guide selection decisions across registries.

