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.
John Hertler trained Ballindaggin, who won the inaugural running of the Molson Export Challenge (Woodbine Mile) in 1988 and Slew the Dragon who won the 1988 Hollywood Derby.
However, he is best known as the trainer of the Eclipse Award winner and Hall of Fame colt, Slew o' Gold.
This American horse racing biographical article is a stub.