It was an O’Brien one-two as 100-30 shot Magician was followed to the line by Gale Force Ten, who was second.
Trading Leather finished in third as Magician, who won the Dee Stakes at Chester, send the crowd into raptures at the Curragh.
The winner has been entered in the Derby at Epsom on June 1 and the St James’s Palace Stakes at Royal Ascot.
In the day's other big race, the Betfred Temple Stakes at Haydock, Kingsgate Native sprung a surprise by coming in a 14-1 winner by a neck from Swiss Spirit (9-1).
Reckless Abandon finished third a head behind the winner at 3-1 in a thrilling race, with hot favourite Sole Power (11-10) coming in fourth of the 10 runners.