Fyldener (1803–1829) was a British Thoroughbred racehorse and sire best known for winning the classic St Leger Stakes in 1806. In a racing career which lasted from June 1806 until June 1809 he won six times from ten competitive starts. As a three-year-old, Fyldener won his first four races, culminating with a win in the St Leger at Doncaster Racecourse. He failed to win in an abbreviated 1807 season and missed the whole of 1808, before returning as a six-year-old in 1809 to win his last two races. After his retirement from racing he had a long, but relatively undistinguished career as a breeding stallion.