Robert Ng's Romanised, a 25-1 longshot in a field of 11, shocked the Tattersalls Irish Two Thousand Guineas (G1) May 26 at the Curragh.
The Ken Condon-trained colt, a son of Holy Roman Emperor, came from well off the pace under Shane Foley to collar U S Navy Flag and win by 2 1/4 lengths.
The final time for the mile test on a track rated good to firm was 1:38.93.
Romanised endured a bad trip when he finished sixth in the Coolmore Zoffany Irish EBF Tetrarch Stakes at Naas this month and had not won since his maiden debut in April of 2017. Condon had not saddled a winner this year.
"We always thought a lot of him, and to win a classic on our doorstep is a dream come true," Condon said. "Romanised wasn't there physically as a 2-year-old, and it just wasn't happening for him earlier in the spring, but he liked the drying ground and he worked really well on Tuesday.
"It's going to take a day or two for this all to sink in. It's pretty special to step through the door, which doesn't open for many, and train a classic winner."
Foley, who landed his second classic after he took the 2016 Tattersalls Irish One Thousand Guineas (G1) on Jet Setting, was also thrilled.
"I've always liked this horse, and to come back after the last day was great. I was quietly confident, and the plan was to get him relaxed," Foley said. "I nursed him around, and he picked up well. Ken had stood by me as an apprentice, and I'm delighted to ride a classic winner for him."
U S Navy Flag grabbed the lead early and looked set to give trainer Aidan O'Brien a record-extending 12th win in the race for much of the straight, but he had no response when the winner swept by. O'Brien was also responsible for the next two home, third-place Gustav Klimt and fourth-place Threeandfourpence.
"It's great for Ken," O'Brien said. "Our horses ran well, and it would be hard to say US Navy Flag didn't get the trip. That being said, he probably just about gets the mile, and seven furlongs might be his optimum. He has a few entries at Ascot, and we'll wait and see."
The Mark Johnston-trained Elarqam, a 2-1 favorite after finishing fourth in the QIPCO Two Thousand Guineas (G1) at Newmarket, came home a disappointing sixth.
"It was too bad to be true," Johnston said. "We'll take him home and see if anything comes to light."