Epsom Derby runner-up Treasure Beach went one better to give trainer Aidan O'Brien his ninth Irish Derby victory.
The Queen's horse Carlton House, third at Epsom, was sent off the 5-4 favourite but could only finish fourth.
O'Brien landed a 1-2-3 at the Curragh, with Seville (5-1) in second and Memphis Tennessee (10-1) third.
Chester Vase winner Treasure Beach was giving 41-year-old O'Brien his sixth consecutive victory in the race.
It was a major improvement for Seville after finishing sixth at Epsom, while Memphis Tennessee had finished fourth on 4 June after setting a cracking pace.
In Sunday's showpiece, Colm O'Donoghue settled Treasure Beach in fourth for much of the mile-and-a-half contest, with his stablemate Memphis Tennessee, under O'Brien's son Joseph, setting the pace.
There were still plenty in with a chance turning for home, with Seville, ridden by Seamie Heffernan, and Sir Michael Stoute's Carlton House seemingly travelling best.
But Stoute's charge could not pick up for Ryan Moore when it mattered, and it was Seville and Treasure Beach who fought out the finish, with the latter emerging triumphant by three-quarters of a length.
Carlton House slipped off the pace in the closing stages
Treasure Beach was a 25-1 shot when beaten by a head by Pour Moi at Epsom, but showed that performance was no fluke to give O'Donoghue his first Irish Derby success.
O'Brien said: "Memphis Tennesse set a nice, even pace and it seemed to suit all the horses.
"Colm was excellent on Treasure Beach and settled him beautifully before producing him brilliantly.
"Treasure Beach has progressed with every run and he has a few options now - he could go for the Grand Prix de Paris at Longchamp, the King George [Ascot], or else he could have a break before coming back for the second half of the season.
"We are very lucky in that his owners have decided to keep their horses in training as four-year-olds, and that gives us options with giving the three-year-olds breaks."
John Warren, racing manager for the Queen, said Carlton House ran "flat" and is likely to be dropped in distance to a mile and a quarter.