Trained by Aidan O’Brien, the daughter of Galileo (10-1) was having only the third start of her career in the Classic, having finished only sixth on her latest appearance in the Leopardstown trial on 30 March.
Lightning Thunder, agonisingly beaten by Miss France at Newmarket, ran a fine race once again, but simply had no answer to the thrust of Marvellous, who shot three lengths clear.
The Olly Stevens-trained Lightning Thunder had finished fast and late on the Rowley Mile but Harry Bentley sat more prominently in mid-division as Marvellous’s stablemate, Wonderfully, made the running.
Bentley swept to the lead with a couple of furlongs remaining, but Marvellous was too strong as O’Brien reached the roll of honour for the sixth time in his career.
James Doyle, who won Saturday’s 2000 Guineas on Kingman, finished third aboard the Dermot Weld-trained Vote Often.
Marvellous was subsequently slashed to around the 10-1 mark for the Investec Oaks.
O’Brien said: “She handled this sort of ground when she won her maiden at Navan last year.
“She then had the one run this year at Leopardstown and had a bit of a break after that as, like a lot of mine, she was coughing a bit.
“Joseph (O’Brien, rider of stablemate Palace) had a tough choice and he knew it was a close call, but at declaration time we didn’t think it was going to get as soft as this.
“With Marvellous, the plan was to come here and then on to Epsom. You’d have to say she’d definitely get a mile and a quarter the way she ran to the line.
“She’s a nice, compact filly and I don’t think she’d have any problems handling Epsom.”
Owner John Magnier said: “Aidan fancied her. In fact, I think he even asked Joseph to ride her and Joseph picked the other one.
“Her pedigree would indicate there could be more to come. She’s out of a sister to Giant’s Causeway who won the Cherry Hinton.
“She’s really well bred and probably bred to get a mile and a half.
“We’ll have to listen to what they all say over the next few days but I couldn’t see any reason why not (run in the Oaks) if all goes well.”
Lady Cecil’s Noble Mission continued his incredible transformation with a first Group One victory in the Tattersalls Gold Cup at the Curragh.
It is only at the age of five that Frankel’s younger brother has started to emerge from his sibling’s shadow and he reaped the benefit of an aggressive ride by James Doyle, also successful in the colours of Khalid Abdullah on Kingman in Saturday’s Tattersalls Irish 2,000 Guineas.
Noble Mission and Magician went off the even-money joint-favourites and the runner-up was closing by the post.
Meanwhile, in Paris, Cirrus Des Aigles turned in a masterclass from the front to gamely account for Olympic Glory in the Prix d’Ispahan at Longchamp.
In what was billed as a clash between the alleged big two, the Richard Hannon-trained Olympic Glory could finish only fourth under Frankie Dettori.
Cirrus Des Aigles had defeated Arc winner Treve on his last start, but this time made virtually every yard of the running in the hands of Christophe Soumillon.
The Corine Barande-Barbe-trained eight-year-old was pressed by the revitalised Anodin, but Soumillon had far too much class beneath him and eased home inside the final 100 yards.
Pollyana finished third, while Olympic Glory was hard at work a couple of furlongs from home on his first try over nine furlongs and folded meekly late on.