Herod was a Thoroughbred racehorse. He was one of the three foundation sires of the modern Thoroughbred racehorse, along with Matchem and Eclipse. Herod was the foundation sire responsible for keeping the Byerley Turk sire-line alive.

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.