Grey Swallow won the Budweiser Irish Derby from the favourite North Light at the Curragh.
Grey Swallow and Pat Smullen beat the favourite North Light (left)
Jockey Pat Smullen tracked the leaders in the middle of the pack and took him clear from one furlong out to land the Classic for three-year-olds.
The Dermot Weld-trained colt showed superior staying power to overhaul the English Derby winner.
The 10-1 shot won by half a length from the 8-11 favourite with rank outsider Tycoon third.
Moscow Ballet set the early pace in the one-mile, four-furlong race with Frankie Dettori's mount Rule of Law taking up a good position in second.
Unhappy with the easy pace, Kieren Fallon moved North Light up on the outside at the final bend and made his challenge from two furlongs out.
Epsom Derby runner-up Rule of Law gave chase but it was Grey Swallow who thundered down the outside to claim a famous win.
Smullen told BBC Sport: "I can't believe it. We had so much faith in this horse
in the English and Irish Guineas, but obviously all he wanted was a little bit
further. He's a champion.
"Words can't describe this. I've had an up and down year so far, but winning
races like this is what it's all about. For the boss as well, and all the boys
at home. It's unbelievable."
The 150-1 outsider Tycoon put in a late run to snatch third from Rule Of Law,
who again beat the Epsom third Let The Lion Roar.
Grey Swallow was fourth in the English 2,000 Guineas and third in the Irish equivalent earlier this season, and was attempting a trip longer than a mile for the first time.
Weld said: "I've always believed in this horse. There were doubts about him
staying a mile and a half, but he worked superbly the other day and I knew I had
him in good form.
"This was a very good Derby and an extra special win as he was bred by my
mother, who also owns part of him."
Budweiser Irish Derby
Group One, 1m 4f
1 Grey Swallow (P Smullen) 10-1
2 North Light (K Fallon) 8-11f
3 Tycoon (C O'Donoghue) 150-1