Horse races vary widely in format and many countries have developed their own particular traditions around the sport. Variations include restricting races to particular breeds, running over obstacles, running over different distances, running on different track surfaces and running in different gaits.
While horses are sometimes raced purely for sport, a major part of horse racing's interest and economic importance is in the gambling associated with it, an activity that in 2008 generated a worldwide market worth around US$115 billion.
Horse racing has a long and distinguished history and has been practised in civilisations across the world since ancient times. Archaeological records indicate that horse racing occurred in Ancient Greece, Babylon, Syria, and Egypt. It also plays an important part of myth and legend, such as the contest between the steeds of the god Odin and the giant Hrungnir in Norse mythology.
Chariot racing was one of the most popular ancient Greek, Roman and Byzantine sports. Both chariot and mounted horse racing were events in the ancient Greek Olympics by 648 BC and were important in the other Panhellenic Games. This was despite the fact that chariot racing was often dangerous to both driver and horse as they frequently suffered serious injury and even death. In the Roman Empire, chariot and mounted horse racing were major industries, and from the mid-fifteenth century until 1882, spring carnival in Rome closed with a horse race. Fifteen to 20 riderless horses, originally imported from the Barbary Coast of North Africa, ran the length of the Via del Corso, a long, straight city street, in about 2½ minutes.
In later times, Thoroughbred racing became, and remains, popular with the aristocrats and royalty of British society, earning it the title "Sport of Kings".
Historically, equestrians honed their skills through games and races. Equestrian sports provided entertainment for crowds and honed the excellent horsemanship that was needed in battle. Horse racing of all types evolved from impromptu competitions between riders or drivers. The various forms of competition, requiring demanding and specialized skills from both horse and rider, resulted in the systematic development of specialized breeds and equipment for each sport. The popularity of equestrian sports through the centuries has resulted in the preservation of skills that would otherwise have disappeared after horses stopped being used in combat.
There are many different types of horse racing, including: