Samuel Doyle Riddle (July 1, 1861 – January 8, 1951) was an American businessman and racehorse owner. He was born in Glen Riddle, Pennsylvania, a small town southwest of Philadelphia given the family name by his father. Riddle married Elizabeth "Lizzie" Dobson in 1883. She was the daughter of John Dobson, who with his brother owned a mill in East Falls, Philadelphia. Riddle and Elizabeth had no children, but raised Elizabeth's niece, Sarah Dobson Fiske, the daughter of Elizabeth's sister, Sarah Dobson Fiske.