A horse race is a sporting event in which horses compete around a track. The course can be flat or over a course of jumps, and the horses may be ridden or driven. Spectators frequently place bets on the outcome of the race, which has made horse racing an industry. The sport has been impacted by technological advances in recent years, but it retains the vast majority of its traditions and rules.

Several types of horse races are run, each with its own set of rules. Some are open to all horses regardless of age, sex, birthplace, or previous performance, while others have specific requirements such as a minimum weight or a number of wins. The most famous of these events is the Triple Crown, which is awarded each year to a champion thoroughbred horse in the United States.

The exact origin of organized horse racing is not known, but it has been documented throughout history. Four-hitch chariot and mounted (bareback) races were prominent in the Olympic Games in ancient Greece between 700-40 bce, and a sport of mounting riders on specially prepared horses was developed by the Persians.

Modern racing is largely dominated by countries with a long tradition of breeding and racing thoroughbreds, including Ireland, England, France, Australia, and the United States. Flat races are run over a variety of surfaces, including turf, dirt, and artificial materials such as Polytrack. Jumps races are also popular in some regions and use a wide range of tack and equipment.

In the United States, organized horse racing began with the British occupation of New Amsterdam in 1664. Colonel Richard Nicolls laid out a 2-mile (3-kilometer) course on the plains of Long Island and offered a silver cup for the winner. This was the first of many such races, establishing a system of racing centered on stamina rather than speed.

The most prestigious races are called stakes or graded stakes in the United States, conditions races in England and France, and group races in Australia and New Zealand. These have the biggest purses, and are generally weight-for-age races with some allowances for younger horses or females against males. There are also races called handicaps, in which all horses are assigned the same weight for fairness but a few receive extra weight in recognition of their better ability.

The racing industry has come under increasing scrutiny from animal welfare groups who claim that the sport is cruel to horses, often putting them at risk of injury and even death on the track. Injuries are common, especially if horses are raced before they are fully mature, and the high speeds involved can cause cracked leg bones and hooves. Some horses are even shipped from America to foreign slaughterhouses for sale as dog food and other products. The industry is working to address these concerns, and has made some improvements. But some believe that the sport needs to undergo further reforms, such as instituting mandatory drug testing and banning equine doping.