Paris Saint-Germain slipped to their first loss of the Ligue 1 season despite a Kylian Mbappe double as impressive Nice secured a 3-2 victory at the Parc des Princes on Friday, with Terem Moffi scoring twice.
PSG fell behind less than midway through the first half as Moffi found the net following a poor mistake by Mbappe.
The France striker made amends on the half-hour mark, but Gaetan Laborde restored Nice's lead eight minutes after the break and Moffi put another past the ragged hosts.
Mbappe volleyed home to give the reigning French champions hope but Nice held on.
Luis Enrique's PSG, who would have usurped Monaco at the top with three points, instead slipped to third in the early table with eight points from five games, one point behind unbeaten Nice.
"Throughout the match they were fresher than us," said Luis Enrique after his first loss as PSG coach.
"Obviously a defeat hurts, we all have to improve, myself included. But I liked our state of mind.
"Of the three goals, two were deflected. Nice played great football, but I'm not worried and I saw the fans support their team even when they were two goals down."
Nice, backed by British billionaire Jim Ratcliffe, are hoping to bounce back this term from a disappointing campaign last season when they could only finish ninth in Ligue 1.
"Everything must be perfect to get a result here, the opponents must not be at their level, and we must give a complete performance," Nice coach Francesco Farioli said.
"Beyond the tactical aspects, I saw a team of warriors."
- Verratti farewell -
Before kick-off, the Parc des Princes bade farewell to Marco Verratti after he ended his 11-year stay at PSG to move to Qatari club Al-Arabi.
Messages from former teammates including Zlatan Ibrahimovic and Thiago Silva were played on the big screen, while Verratti was allowed a lap of honour around the pitch.
The Italian midfielder made 416 appearances for PSG, winning nine Ligue 1 titles and six French Cups, but failed to help the club to a maiden Champions League triumph.
Nice dampened the party atmosphere by taking a shock lead in the 21st minute as PSG played themselves into trouble at the back.
Mbappe dropped deep inside his own half to take possession but immediately gave it away in a dangerous area and the ball bounced kindly for Moffi whose shot took a big deflection off Milan Skriniar and spun into the net.
The visitors came close to doubling their advantage when Khephren Thuram's shot was well saved by PSG goalkeeper Gianluigi Donnarumma.
Mbappe made an impact at the right end of the pitch as he grabbed his sixth league goal in four appearances this season, slamming a powerful shot from Achraf Hakimi's cut-back through a poor attempted save from Nice 'keeper Marcin Bulka.
PSG started to dominate but almost went into the break behind when Jordan Lotomba blasted an excellent opportunity over the bar with the final kick of the first half.
Nice did restore their advantage in the 53rd minute, though, as Moffi played in Laborde to slot past Donnarumma.
Paris continued to ship chance after chance at the back and Moffi all but ended the game as a contest with 21 minutes left.
The PSG defence backed off the Nigerian striker and he took his time before stroking a low finish into the bottom corner from outside the area.
Mbappe acrobatically volleyed into the far corner after good work from substitute Randal Kolo Muani on his debut, but Nice saw out the closing moments with relative ease.
PSG will now have to raise themselves before their Champions League group-stage opener against Borussia Dortmund on Tuesday.
