Birdstone (foaled May 16, 2001, in Kentucky) is an American Thoroughbred racehorse best known for winning the 2004 Belmont Stakes and has become a successful sire.Owned and bred by Marylou Whitney of Whitney family racing fame, Birdstone won the Champagne Stakes, a leading race for two-year-olds, at Belmont Park in 2003, but was not a factor in the first two Triple Crown races (finishing eighth in the Kentucky Derby and skipping the Preakness Stakes) and was a 36-1 longshot when he upset the overwhelmingly favored Smarty Jones, taking the lead in the final furlong (201 m) in the fastest Belmont since the advent of modern electronic timing (2002 was the first year times were kept to hundredths).His sire Grindstone won the Kentucky Derby in 1996 and was a son of 1990 Derby winner Unbridled.