Dual Derby winner Galileo will run his last race in tomorrow week's Breeders' Cup Classic at Belmont Park in New York.
Hopes that the three-year-old would be back in action next season have been dashed by an announcement that he is to be retired to stand as a stallion at Coolmore Stud.
The Aidan O'Brien-trained colt will be joined there by July Cup-winning stable-companion Mozart, who is also due to sign off in the Breeders' Cup, and Golan, who lifted the 2000 Guineas for Sir Michael Stoute in May.
No stud fee has yet been set for Galileo, who also won the King George VI and Queen Elizabeth Diamond Stakes at Ascot before meeting his only defeat to date when narrowly beaten by Fantastic Light in the Irish Champion Stakes.
Derby winners are invariably retired to stud after their Classic season nowadays, with only four in the past 20 years racing on at four.
Of those to have remained in training High-Rise, Quest For Fame and Slip Anchor failed to enhance their reputation but 1983 Epsom scorer Teenoso boosted his record by returning to land the King George the following year.