Study Of Man claimed Classic glory in the Qipco Prix du Jockey Club at Chantilly.
Pascal Bary’s colt was among the leading contenders following an impressive display in the Prix Greffulhe at Saint-Cloud last month and was always travelling strongly in midfield.
He began to reel in the leaders early in the home straight under Stephane Pasquier and battled his way to the lead inside the final furlong.
Several horses attempted to peg him back as the post loomed, but Study Of Man, a son of Deep Impact, clung on for victory.
James Tate’s French 2000 Guineas runner-up Hey Gaman looked set to play a significant part for a long way before fading late in the piece. His Poule d’Essai des Poulains conqueror Olmedo, however, was bitterly disappointing.
Key Victory came up short in his bid to provide trainer Charlie Appleby, jockey William Buick and Sheikh Mohammed’s Godolphin operation with a second Derby success in the space of 24 hours following Masar’s triumph at Epsom on Saturday.
Aidan O’Brien saddled a quartet of runners in Flag Of Honour, Hunting Horn, Kenya and Rostropovich, but all finished unplaced.
Betfair cut the winner to 20-1 from 33-1 for the Prix de l’Arc de Triomphe at ParisLongchamp in October.
Alan Cooper, racing manager to winning owners the Niarchos family, said: “He did it very well and he’s shown what Pascal and Stephane have always thought of him was correct – he’s a top-class horse.
“After he won the Prix Greffulhe it was either come here or go to Epsom (for the Investec Derby) and we decided to stay at this distance (mile and a quarter) for the moment.
“We’ll regroup now and see whether he could be a horse for the Prix de l’Arc de Triomphe, but let’s not jump to any conclusions.
“We’ll get him back and get ourselves back and go from there.”
Bary said: “He’s a fantastic colt and has it all in terms of pedigree and class. I’m speechless.”
Pasquier added: “It’s incredible and he’s a super colt with a lot of heart. It wasn’t a race tailor-made for him as I had to make more use of him than ideal.
“He showed his fighting qualities to the very end as he’s better than the rest.
“It’s now full steam ahead to the Arc!”