Octavius (1809–1831) was a British Thoroughbred racehorse and sire. In a racing career that lasted from April 1812 to May 1814 he ran thirteen times and won four races. He recorded his most important success when winning the Derby. Octavius remained in training for two more seasons, his best subsequent performance coming when he won the Epsom Gold Cup as a four-year-old in 1813. At the end of 1814 Octavius was retired to stud where he had moderate success as a sire of winners.