Equestrian sports are among those contested at the Summer Olympic Games. Equine events began at the Olympics in 1900, when competitions in polo (considered by the International Olympic Committee (IOC) to be a separate sport from the other equestrian events), vaulting, four-in-hand driving, mail coach driving, mixed hacks and hunters and three types of jumping (high jump, long jump and show-jumping) were held.^[1][2] Most of these events were later discontinued, although equestrian events have continued through the 2016 Summer Olympics, and now include team and individual dressage, three-day eventing and show-jumping.^[3] Competitors in the modern pentathlon event also have to complete an equestrian show-jumping course, but this is not part of the equestrian events.^[4]

Modern-day Olympic equestrian events are rooted in cavalry skills and classical horsemanship,^[5] and through 1948, competition was restricted to active-duty officers on military horses.^[6] Only after 1952, as mechanization of warfare reduced the number of military riders, were civilian riders allowed to compete.^[7][8] Equestrian is the only Olympic sport in which animals compete with humans, and is one of four sports in which the genders compete against each other,^[9] the others being some sailing divisions, mixed doubles division in tennis and the mixed doubles division of badminton.^[10][11] The rules for Olympic equestrian competition are set by the Fédération Équestre Internationale, the international governing body for equestrian sports.^[3]

In two instances, the equestrian portion of the Olympics has been held in a different location from the rest of the games. The first was during the 1956 Summer Olympics in Melbourne, Australia when, due to Australian quarantine laws, the equestrian portion was held in Stockholm, Sweden. At the next IOC meeting, it was decided to hold a special Equestrian Olympic Games several months before the actual Olympics, complete with its own opening and closing ceremonies.^[12] This meant that Switzerland, which had officially boycotted the 1956 Games because of the Soviet Union's recent invasion of Hungary, still brought home a medal because of its participation in the equestrian portion several months earlier.^[12][13] The second instance was during the 2008 Summer Olympics, when the equestrian events were held in Hong Kong rather than Beijing. This decision was made when, in 2005, international veterinary groups refused to certify the main Olympic city as free of equine diseases. This would have resulted in horses leaving Beijing after the games and having to go through lengthy quarantine processes before being allowed to re-enter their home countries. Hong Kong also had the benefit of having better facilities, including a top equine hospital and one of only a few equine drug-testing labs in the world.^[14]

The Summer Olympics have included 2,129 equestrian participants, including 1,751 men and 378 women, from 69 countries.^{[1][note 1]}, of which 564 won a medal. As of the 2008 Olympics, 395 medals have been awarded to 31 NOCs. The oldest rider was 72-year-old Arthur von Pongracz of Austria at the 1936 Summer Olympics, while the youngest was 16-year-old Luiza Almeida of Brazil at the 2008 Summer Olympics.^[1] The leading medalist is Isabell Werth of Germany (10, 6 gold), followed by Anky van Grunsven of the Netherlands (9, 3 gold) and Reiner Klimke of Germany (8, 6 gold). Germany leads the country medalist rankings with 25 gold medals (52 overall),^{[note 2]} followed by Sweden with 17 (43 overall) and France with 14 (37 overall).^[1] Canadian rider Ian Millar holds the record for the most Olympic equestrian appearances and matches the record for athletes in any sport, having competed in ten Olympics as of 2012.^[15]