John W. Sadler (born July 30, 1956) is an American horse trainer in the sport of Thoroughbred horse racing. He’s got over 2,600 race wins, including the 2018 Breeders' Cup Classic with Accelerate, who was subsequently named American Horse of the Year. He has won multiple training titles at Santa Anita Park, Del Mar and the now defunct Hollywood Park. Sadler trained Flightline, the winner of the 2022 Breeders' Cup Classic.