Eclipse was an undefeated 18th-century British Thoroughbred racehorse who won 18 races, including 11 King's Plates. He raced before the introduction of the British Classic Races, at a time when four-mile heat racing was the norm. He was considered the greatest racehorse of his time and the expression, "Eclipse first, the rest nowhere" entered the English vernacular as an expression of dominance.

The Thoroughbred is a horse breed developed for horse racing. Although the word thoroughbred is sometimes used to refer to any breed of purebred horse, it technically refers only to the Thoroughbred breed. Thoroughbreds are considered "hot-blooded" horses that are known for their agility, speed, and spirit.