Alydar was an American Thoroughbred race horse and sire. A chestnut colt, he was most famous for finishing a close second to Affirmed in all three races of the 1978 Triple Crown. With each successive race, Alydar narrowed Affirmed's margin of victory; Affirmed won by 1.5 lengths in the Kentucky Derby, by a neck in the Preakness and by a head in the Belmont Stakes. Alydar has been described as the best horse in the history of Thoroughbred racing never to have won a championship. Alydar's fame continued when he got older. He died under suspicious circumstances.

Affirmed was a champion American Thoroughbred racehorse who is the eleventh winner of the American Triple Crown. Affirmed was well known for his famous rivalry with Alydar, whom he met ten times, including Alydar coming second in each of the three 1978 Triple Crown races. After Affirmed won the Triple Crown, there was a 37-year wait until American Pharoah swept the series in 2015.