A horse race is a contest of speed or stamina between horses over an open course. It can involve a single or multiple races and may be conducted on the flat or over jumps. The first horse across the finish line is declared the winner of the race. While the sport has evolved from a primitive wager between two horses to a complex spectacle involving large fields, sophisticated electronic monitoring equipment, and enormous sums of money, its basic concept remains unchanged. Critics contend that horse racing is inhumane or corrupted by drug abuse and overbreeding, while advocates point out that the sport represents a pinnacle of achievement for competitors.

While it is not certain when the first horse race took place, both chariot and mounted (bareback) horse races were featured in the ancient Olympic Games of Greece between 700-40 bce. By the time of Louis XIV of France (reigned 1643-1715), racing had become a popular diversion among members of the upper classes. Louis XIV established a centralized system of regulation and organization, requiring certificates of pedigree for all horses and imposing extra weight on foreign horses in order to discourage gambling.

Historically, the main types of horse races have been handicaps, in which the weights that all horses must carry are adjusted according to specific criteria such as age, distance, or sex. The goal of the handicap system is to render all horses as nearly equal as possible in the context of the specific race, thus repudiating the classic notion that the best horse should win. This approach is still in use in many parts of the world, and it has helped to broaden the appeal of horse racing as a form of entertainment.

Flat races can be run over a variety of distances and courses, and there are numerous variations in the rules that govern them. For example, some races are run over one mile, while others require a full two miles to complete. In addition, there are different types of jump races, such as hurdles and steeplechases, which may have one or more obstacles.

Betting is a vital part of the horse race experience, and fans can place a variety of bets on their favorite horses. Bets can be placed to win, to place, or in accumulators in which bets on several horses are combined to determine the outcome of the race. Generally, all horse races must begin from starting stalls or a starting gate, although they can be started with a flag in exceptional or emergency circumstances.

Horse race betting is a lucrative business, and it accounts for a significant percentage of total turnover at many racetracks. In the United States, horse race bets were tallied manually until 1984, but a computerized pari-mutuel betting system greatly increased both turnover and attendance. The development of televised horse racing and the introduction of a standardized bet size also contributed to the growth of the sport.