Multiple Group 1-winner Ghaiyyath has been retired to stud.
Godolphin have made the decision after the 5-year old showed some muscle soreness following a routine piece of work.
Three of Ghaiyyath's four Group 1 victories came in 2020 alone, most recently in the Juddmonte International Stakes at York in August.
His last outing was at last month's Irish Champion Stakes at Leopardstown where he placed 2nd behind the Aidan O'Brien-trained Magical.
He had been set to travel to the Breeders Cup, but trainer Charlie Appleby reported some soreness behind at the weekend.
"Ghaiyyath has had a fantastic career, winning nine of his 13 races," Appleby said, "His high-class cruising speed and relentless style of galloping was a joy to watch and as I have said before, this year he came together both physically and mentally and looked the finished article.
"It is obviously disappointing not to be taking him to the Breeders' Cup but the exertions of a long season, which started in Dubai in January, were starting to show and the decision has been made to retire him.
“He was an outstanding part of the Moulton Paddocks team and I know that his numerous top-level successes gave our Principal, His Highness Sheikh Mohammed, a great deal of pleasure."
Managing director of Godolphin Ireland Joe Osborne added, "Ghaiyyath is a great addition to our roster: his superior ability as a racehorse combined with his looks and his pedigree will make him a sought-after option for breeders.
"We are delighted he will be standing at Kildangan Stud next season."