Iron Constitution (1974-1989) was an American Thoroughbred racehorse owned by Harry T. Mangurian Jr.'s Mockingbird Farm of Ocala, Florida. Iron Constitution won the 1977 Withers Stakes and placed second three weeks later in the $200,000 grade 1 1977 Preakness Stakes to undefeated Seattle Slew who would go on to win that year's U.S. Triple Crown.