Anthony Sawyer "Tony" Horton, Jr. is an American fitness trainer best known for the boot camp style P90X home fitness program.
Horton was raised in Trumbull, Connecticut, and attended the University of Rhode Island. By 1980, he had moved to Los Angeles with the intention of becoming an actor. For a time, he also performed as a stand-up comedian. He began working out at the World Gym in Venice, California, which had been frequented by professional bodybuilders such as Arnold Schwarzenegger and Lou Ferrigno. In an attempt to avoid the bulky, non-flexible bodybuilder look, Horton focused more on exercise routines to bring about speed, flexibility, and balance, as well as muscle growth. Later, he collaborated with former-triathlete and Ironman competitor Mark Sisson, who introduced him to interval training.
During the early 1980s, Horton became a personal trainer and established his business, ASH Fitness, in Santa Monica. He began to gather a list of clients that included celebrities such as Billy Idol, Tom Petty, Lindsey Buckingham, Stevie Nicks, Shirley MacLaine, Sean Connery, Annie Lennox, Rob Lowe, Antonio Banderas, and Bruce Springsteen.