Nice came into the game in concerning form under new boss Franck Haise, winning just one of their first four league games under the Frenchman (D1, L2).
Despite this, Les Aiglons started the game on the front foot and found themselves ahead after just four minutes, when Dylan Batubinsika turned Jonathan Clauss’ cross into his own net.
Things quickly got worse for the visitors too, finding themselves two goals down just three minutes later. This time the goal came from Tanguy Ndombele after Mohamed-Ali Cho’s cross was cleared to the centre of the box, where Ndombele was waiting to fire a powerful effort past Gautier Larsonneur.
Midway through the half, Nice had their third, as Cho got himself on the scoresheet, with the attacker cutting in on his left foot before bending an exquisite strike into the far bottom corner from outside the penalty area.
Haise’s side were running rampant in the first half, and netted their fourth just two minutes later through Youssoufa Moukoko, after the German marked his full debut by heading home his first goal for the club from a yard out.
Saint-Etienne Capitulated even more after that, allowing Evann Guessand to run through on goal before placing the ball in the far bottom-right corner.
Moukoko got his second just before half-time after he received the ball from Guessand and slotted past Larsonneur.
Les Aiglons really took their foot off the gas in the second half, seeming content to just sit on their six-goal lead from the first half.
But the visitors went close to scoring a consolation goal with just under 20 minutes to play, when Benjamin Old took the ball under control before firing goalwards from distance, only to be denied by the woodwork.
Nice did manage to add another goal though shortly after. This time Sofian Diop was the goalscorer after the Moroccan finished off a swift move by the hosts by tapping in the ball from inside the six-yard box.
Haise’s men added an eighth late on when Pablo Rosario dispatched a penalty following Dennis Appiah’s foul on Youssouf Ndayishimiye.
Nice saw out the rest of the game with ease, as they climbed up to fifth in Ligue 1 ahead of the weekend's fixtures.
Meanwhile, Saint-Etienne’s return to the top flight continued to prove difficult as they fell to their biggest defeat since their 9-0 defeat to FC Girondins Bordeaux in 1951.
Flashscore Man of the Match: Youssoufa Moukoko (OGC Nice)