Sea The Stars, who won French Prix de L'Arc de Triomphe on October 4, has been retired.
The 3-year-old colt galloped into the history books by becoming the first horse to win Europe's top three races, after winning the 2,000 Guineas and the Epsom Derby.
Sea the Stars had been touted as a possible entrant in November's Breeder's Cup Classic at Santa Anita in California on November 7, but the retirement announcement has put paid to the legendary horse running in the States.
The Prix was the sixth victory for Sea the Stars in a Group One race and puts him on par with some of Europe's greatest racehorses.
Jockey Mick Kinane, 50, was on board See that Stars for the Prix win, and won the race for the third time after first winning it 20 years ago on Carroll House and 10 years ago on Montjeu.
Trainer John Oxx told British newspaper The Guardian about the circumstances around the decision to retire the horse;
"It has been decided after discussions with [owner] Mr. Christopher Tsui that Sea The Stars will not take part in the Breeders' Cup at Santa Anita on 7 November. He's had a long season and has been in regular fast work from 3 March, with his final workout on 2 October. He's been in intensive training for seven months with only a three-week break after the Eclipse Stakes at the beginning of July.
"We feel it is unfair to keep him going any further given his unprecedented record of achievement in the last six months. He's come out of the Prix de l'Arc de Triomphe in his usual good form. He is fit and healthy and has been cantering since the race. He is now retiring from racing, but I have no information on stud career details and an announcement will be made at a much later date when plans have been finalized."