The Thoroughbred Times, without naming sources, reported that Frankel died after a lengthy battle with leukemia, while The Horse reported Juddmonte Farms racing manager Garrett O'Roarke as saying that Frankel's ex-wife and daughter were by his side at the time of his death.
Frankel won the Eclipse Award five times, including four starting in 2000 when his barn won 22 graded stakes at 10 tracks and finished second in the Kentucky Derby and Belmont Stakes with Aptitude, The Thoroughbred Times reported.
"Bobby Frankel was one of the greatest trainers in Thoroughbred racing history," said Alex Waldrop, president and CEO of the National Thoroughbred Racing Association. "His outstanding horsemanship, coupled with a keen insight into the game, made him a force in the sport for the last 40 years. His immense talent, and his abiding love for his horses, will be sorely missed."
While saddling six Breeders' Cup winners, Frankel won just one Triple Crown race -- the 2003 Belmont Stakes with Empire Maker to deny Funny Cide a Triple Crown.
Frankel's horses won 3,654 races in 17,657 starts, earning $227,947,775.