The well-backed Blue Bunting, delivered at the last moment along the rail by Frankie Dettori, won the 1,000 Guineas at Newmarket at odds of 16-1.
The Godolphin horse, trained by Mohammad Al Zarooni, was well back in the field approaching the finish.
But Dettori produced a late burst as others laboured in front, and it was left to Together (33-1) and Maqaasid (22-1) to take the minor places.
Dettori said afterwards: "We've got The Oaks in mind for this one now."
It was a first Classic winner for Al Zarooni, the second Godolphin trainer to benefit from Sheikh Mohammad's ownership having joined Saeed Bin Suroor last season.
For Dettori, who lives near Newmarket, it was his first 1,000 Guineas winner since Kazzia in 2002 and his 14th British Classic in all.
In glorious sunshine, the French-trained Immortal Verse failed to start the race after a problem entering the stalls, while Memory, the mount of Richard Hughes, was soon trailed off at the rear.
Hooray, a Group 1 winner, took up the running but faded quickly late on, while Together was the first to commit for home.
The Aidan O'Brien-trained filly held off most of her challengers and led by two lengths passing the furlong market, but jockey Colm O'Donoghue was perhaps not counting on the late turn of foot from Blue Bunting.
Dettori drove for the line, judging his sprint finish to perfection to score by three-quarters of a length. Moonlight Cloud, the 9-2 favourite, finished seventh.
Dettori said: "That was great and a pleasant surprise. The lads had been telling me she was working well, but obviously she had a lot to prove on form.
"Things worked out really well as they went a good pace, which was what I needed.
"It's fantastic as I haven't won a Classic for a while. I'm delighted for the Godolphin team. Mahmood told me she was more of an Oaks filly, so whatever she was going to do today was a bonus. To win is fantastic."
Al Zarooni added: "We always thought she was a mile-and-a-half filly and an Oaks filly and she wanted softer ground. Today she has won when we thought everything was wrong She's still an Oaks filly, but she has done very well."
William Hill were quick to slash Blue Bunting's price for The Oaks with the filly now their 3-1 favourite for the Epsom Classic. She is 9-2 from 25-1 with Victor Chandler for the same race while they make Together 12-1 from 25-1.