Sultanina wore down French filly Narniyn to give John Gosden a hat-trick of victories in the Markel Insurance Nassau Stakes at Goodwood.
William Buick's mount stormed past the 7-4 favourite inside the last 100 yards to claim the Group One honours by a length and a half.
Sultanina (11-2) was stepping down in trip after losing her 100 per cent record in the Lancashire Oaks last time, when second to stablemate Pomology.
Irish challenger Venus De Milo was third.
Venus De Milo made the running under Joseph O'Brien and had Lustrous for company after half a mile.
Narniyn made what looked like a winning move when creeping up on the far rail to hit the front over a furlong out.
However, she had no answer to the late thrust of the lightly-raced Sultanina who asserted her authority with a useful turn of foot.
Buick said: "I'm absolutely delighted for everyone - it's fantastic.
"This filly has really stepped up to the plate.
"It was only the fourth run of her life so it was a good training performance.
"We've always held her in high regard, but no-one as high as her owner."
The Nassau is a race Gosden has dominated recently with The Fugue in 2012 and Winsili last year.
Gosden said: "It's lovely. The Aga Khan's filly (Narniyn) is a really good filly to come over and is a tough nut to break.
"The last furlong and a half was a right duel between the pair.
"This filly is very classy and Philippa (Cooper, of owners-breeders Normandie Stud) bred her down the road, just 11 miles from here, and she always told me this filly was the best and I could never work it out.
"I didn't run her until this year as a four-year-old. She's gone and won a maiden, a Group Three, second in a Group Two and now won a Group One, so it's unbelievable.
"We're going to enter her on Tuesday in the fillies' and mares' race on Qipco Champions Day in October.
"I might just freshen her for that and go straight there and bring a fresh filly for the autumn."
Trainer Alain de Royer-Dupre said of the runner-up: "I think the ground was too fast for her, she was changing her legs.
"She did well but she has the capacity to do better.
"Her next race will be the Prix Jean Romanet at Deauville in three weeks."
Venus De Milo is now likely to head to York later this month.
Trainer Aidan O'Brien said: "It was a solid run but she'd prefer going further and she was a little bit at sea on the track as well.
"She wants to be racing so I'd say she will go for the Yorkshire Oaks.
"York will suit her better."