Steven Mark Asmussen is an American Thoroughbred racehorse trainer. Born into a horse racing family, his parents, Keith and Marilyn "Sis" Asmussen, are both trainers who operate El Primero Training Center off the Mines Road in Laredo, the seat of Webb County in south Texas. His older brother, Cash Asmussen, currently a trainer himself, is a retired Eclipse Award-winning jockey and a champion in Europe.
Asmussen began racing at age sixteen as a jockey, competing at racetracks in New Mexico, California, and New York for three years until his height and weight ended his riding career. In 1986 he began training Thoroughbreds and American Quarter Horses in New Mexico. In 2002, he led all trainers in Thoroughbred flat racing with 407 wins then in 2004 set a new record for wins by a trainer with 555, surpassing the previous standard of 496 held since 1976 by Jack Van Berg.
Steve Asmussen's colt, Curlin, finished third in the 2007 Kentucky Derby and beat out Derby-winner Street Sense to win the 2007 Preakness Stakes. Curlin finished second in the 2007 Belmont Stakes to filly Rags to Riches, and went on to take the Breeders' Cup Classic on October 27, 2007, at Monmouth Park in Oceanport, New Jersey. The Breeder's Cup is considered the "Super Bowl" of thoroughbred horseracing. Curlin's regular jockey is Robby Albarado.