Delegator, runner-up to Sea The Stars in the 2000 Guineas in 2009, has died of an apparent heart attack at Overbury Stud.
The 10-year-old started his racing career with trainer Brian Meehan before being bought by Godolphin and moving to Saeed bin Suroor's stable.
His biggest successes came in the Craven Stakes and Duke of York Stakes.
Retired to stud in 2012, Delegator had made a promising start to his stallion career this year.
His first runner, Nazik, was a winner in early May, since when a total of eight of his first crop have been successful.
They are led by Delectation, winner of the Group Three Firth of Clyde Stakes at Ayr, and Accidental Agent, successful in the £150,000 Tattersalls October Auction Stakes at Newmarket.
Overbury manager Simon Sweeting said on the stud's website, www.ovstud.co.uk: "Delegator made a wonderful start and we all had very high hopes for his future.
"If his stock progress as well from two to three as he did, he'll be a sizeable loss to British breeders."