Japanese runner Orfevre settled for second for the second straight year, followed by Intello and Japanese Derby winner Kizuna.
Treve raced well back through much of the race at Longchamp in the Parisian gardens as Joshua Tree led the way. When jockey Thierry Jarnet got her close on the outside at the top of the lane, she quickly rushed to the lead and drew off in total command.
It was the fifth win without a loss for the 3-year-old, French-bred Motivator filly and none of those has been in much question.
"It's like a fairy tale to me," Jarnet said. "I'm lucky to ride this champion."
Christophe Soumillon, who rode Orfevre, said he thought he was in good position entering the stretch run. Then Treve hit another gear and, "I couldn't follow because she did something completely unbelievable," Soumillon said.
The race was widely heralded as one of the best runnings of the Arc in many years. Kizuna won the Japanese Triple Crown and a prep at Longchamp. Ruler of the World, who was nowhere to be found at the end Sunday, took the Epsom Derby earlier this year.
Winning trainer Criquette Head-Maarek, beaming after the race, said, "She's so good. She's the best I've had. I won't be retiring now."