Avenir Certain stamped her class on the Shadwell Prix de la Nonette as she maintained her unbeaten record at Deauville.
Jean-Claude Rouget's star filly won the Poule d'Essai des Pouliches (French 1000 Guineas) and the Prix de Diane (French Oaks) earlier this season but dropped down in class for this Group Two contest.
Gregory Benoist oozed confidence on the three-year-old and came through the middle of the pack to win impressively from stable companion and pacemaker Crisolles.
The Prix de l'Arc de Triomphe could now beckon for the winner, where she would tackle a mile and a half for the first time.
Rouget said: "Avenir Certain is an extraordinary filly, a great champion."
Roger Charlton's Be My Gal, a Group Three winner at the track last month, faded to finish last of the seven runners with Pat Shanahan's Maid Of The Glens just in front of her.
David Simcock's Madame Chiang was a non-runner.
Avenir Certain is now set to head straight for the Arc, instead of running in the Prix Vermeille at Longchamp on 14 September.
Rouget does, however, accept the filly is not guaranteed to get the mile-and-and-a-half trip of the big one on 5 October.
He said: "We are coming to the end of the season and you have to make choices.
"If she was running in the Vermeille I wouldn't have run her in this race.
"My aim is to bring her to the Arc fresh. I am not convinced that she is a true 2,400-metre (mile-and-a-half) filly but her class could compensate for that.
"We have nothing to lose. If she is beaten we can say it is because she didn't stay and if she wins, well, it's a bit early for that.
"We have nothing to lose and everything to win. If she is beaten we will keep her over a 2,000-metre (mile-and-a-quarter) programme as a four-year-old.
"I think she will stay in training, even if she wins the Arc, but that is a conversation to have with the owners.
"It is very rare to get a horse like her so you need to make the most of it, we will worry about breeding later.
"She is a true-race filly, just like Goldikova or Moonlight Cloud."