Last year's 2000 Guineas and dual Derby winner Camelot has been retired, owners Coolmore have announced.
Trained by Aidan O'Brien, the four-year-old won just one of his three starts this season.
Camelot was being trained for the Breeders' Cup Turf next month but was reported by his connections as being found lame this morning.
Unbeaten as a two-year-old, including a Group One win in the Racing Post Trophy, Camelot excelled at three, albeit against a desperately weak Classic crop.
Victory in the 2000 Guineas at Newmarket was followed by a smooth display in the Derby at Epsom before he had to show his courage to win the Irish equivalent.
The son of Montjeu then attempted to become the first horse since Nijinsky to win the Triple Crown but had to settle for a three-quarter-length second to Encke in the St Leger before finishing down the field in the Prix de l'Arc de Triomphe.
After that race he was struck down with a bad bout of colic and while he returned with a Group Three win at the Curragh this season, he finished behind Al Kazeem in the Tattersalls Gold Cup and the Prince of Wales's Stakes at Royal Ascot and did not run again.
Camelot will stand at Coolmore next season, with his fee yet to be announced.