Gelding
A gelding is a castrated male horse. The word comes from the Old Norse geldr ("barren"). A horse is usually gelded to make him more placid, making him easier to control. Many breeders choose to leave only their better animals as stallions; lesser specimens are gelded, to improve the overall quality of the breed. Geldings were once prized by classical steppe warriors for their silence. The Scythians are thought to have been the first people to geld their horses.

In horse racing, castrating a stallion means it loses any breeding value. However, it may be considered worthwhile if the animal is easily distracted by other horses, and therefore not running to his full potential. Geldings are often preferred over stallions, because they are calmer, and more easy to work with, as they are not as fiery; they may also be preferred over mare, because some mares can be sassy, or "marish". Also, the use of mares may be limited during the later months of pregnancy and while caring for the young foal. Geldings are therefore a favorite for many equestrians, especially amateurs. In many breed shows, youth exhibitors (and sometimes ladies) are not permitted to show stallions.

Under British National Hunt (i.e. jump-racing) rules, nearly all participating horses are geldings to minimise the health and safety risk for horses, riders and spectators. In Europe, geldings are excluded from many of the most prestigious flat races including the Classics and the Prix de l'Arc de Triomphe.