John O. Hertler

John O. Hertler (born September 17 1950 in Ridgewood, Queens) is an American Thoroughbred horse trainer.

He was fifteen years old when he began working for Hall of Fame trainer Phil Johnson with whom he remained for thirteen years. In 1978 he went out on his own, training horses he purchased as well as for others.

John Hertler trained Ballindaggin, who won the inaugural running of the Woodbine Mile in 1988 and Slew the Dragon who won the 1988 Hollywood Gold Cup. However, he is best known as the trainer of the Hall of Fame colt, Slew o'Gold,