Antonio (1816–1828) was a British Thoroughbred racehorse and sire best known for winning a controversial race for the classic St Leger Stakes in 1819. The classic was run twice after claims of an irregular start, but Antonio's victory in the original running was eventually allowed to stand. The rest of his racing career, which lasted from April 1819 until May 1822 was relatively undistinguished although he won five other races. After two minor successes in 1820 he missed the whole of the 1821 before returning as a six-year-old to win two races at Chester. He was then retired to stud where he had limited success as a sire of winners before his death in 1828.

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.