Emilius (1820–1847) was a British Thoroughbred racehorse and sire. In a career that lasted from April 1823 to October 1824 he ran ten times and won seven races, including a walkover. As a three-year-old in 1823 he was undefeated in six starts, including the Derby. After a less impressive year in 1824 he was retired to stud and became a highly successful and important breeding stallion.