Mario Balotelli fired a double as Nice stunned reigning Ligue 1 champions Monaco in a 4-0 win at the Allianz Riviera.
Italian striker Balotelli converted an early penalty and struck again in the second half after Alassane Plea had doubled Nice's lead before half-time. Ignatius Ganago's late fourth rounded off a comprehensive victory.
Monaco, who launch their Champions League campaign at RB Leipzig on Wednesday, had opened the domestic season with four straight wins.
But Leonardo Jardim's side were no match for Nice, dumped out of the Champions League before the group stage by Napoli last month and who were securing only their second win of the season.
Balotelli picked himself up to score the opening goal from the penalty spot in the sixth minute after he had been fouled by Djibril Sidibe.
Joao Moutinho went close to equalising for Monaco when he flashed a left-footed shot wide soon after, but Nice doubled their lead in the 18th minute through Plea.
The winger raced on to Allan Saint-Maximin's fine through-ball and crashed home an unstoppable shot into the top corner.
Neither side mustered another clear-cut chance before the break, when Monaco replaced Arsenal transfer target Thomas Lemar and Rony Lopes with Rachid Ghezzal and Guido Carillo.
Nice continued to restrict their frustrated opponents to speculative long-range efforts before extending their lead on the hour mark when Balotelli steered home Arnaud Souquet's cross from six yards.
Kamil Glik and Carrillo both headed narrowly off target in the space of a minute as Monaco responded and Sidibe fired straight at Nice goalkeeper Yoan Cardinale.
Balotelli had been withdrawn to rapturous applause from the home fans in the 74th minute and his replacement Ganago had the final word.
Nice midfielder Pierre Lees-Melou's pass into the area found Ganago in space and the substitute made no mistake from a central position.