Theodore was a British Thoroughbred racehorse and sire best known for winning the classic St Leger Stakes in 1822 at odds of 200/1. Trained in Yorkshire by James Croft, he won the second of his two races as a two-year-old and showed good form the following year, winning races at Catterick, York and Newcastle. His St Leger prospects, however, appeared remote after health problems and poor performances in training gallops. His upset win in the classic, followed by a poor run over the same course and distance two days later, attracted a great deal of comment and suspicions of race-fixing, although none of the allegations was ever proved.

The St Leger Stakes is a Group 1 flat horse race in Great Britain open to three-year-old thoroughbred colts and fillies. It is run at Doncaster over a distance of 1 mile, 6 furlongs and 115 yards, and it is scheduled to take place each year in September.