The American Quarter Horse, or Quarter Horse, is an American breed of horse that excels at sprinting short distances. Its name is derived from its ability to outrun other horse breeds in races of 1⁄4 mi (0.40 km) or less; some have been clocked at speeds up to 44 mph (71 km/h). The development of the Quarter Horse traces to the 1600s.

The American Quarter Horse Association (AQHA), based in Amarillo, Texas, is an international organization dedicated to the preservation, improvement and record-keeping of the American Quarter Horse. The association sanctions many competitive events and maintains the official registry. The organization also houses the American Quarter Horse Hall of Fame and Museum and sponsors educational programs. The organization was founded in 1940 in Fort Worth, Texas, and now has nearly 234,627 members, over 32,000 of whom are international.