Marseille came flying out of the blocks in the opening stages, with Mason Greenwood and Benjamin Pavard linking well.
The visitors were restricted to hopeful balls upfield, though Jeffrey de Lange had to be on his guard after Greenwood’s mistake let in Fode Doucoure.
Le Havre were under the cosh for virtually the entire opening quarter hour as the hosts bombarded them from all sides.
The hosts’ frustration was clear and only increased after Le Havre took the lead out of the blue, thanks to a wonderful slaloming effort and a curling low shot from Yassine Kechta.
On the half hour, OM were handed a lifeline as pressure from Pierre-Emerick Aubameyang tempted Gautier Lloris into handling the ball right on the edge of the box.
An initial yellow card was upgraded to a red after a VAR intervention, and the subsequent penalty kick was dispatched with ease by Greenwood to bring Marseille level.
A numerical advantage meant the hosts had almost total domination of possession from then on. The pressure from the hosts was incessant after the break, but by the hour mark, they still hadn’t managed to break down a resolute Le Havre back line.
A flurry of substitutions for both sides was clearly designed to have a positive effect, and no sooner had Marseille’s Robinio Vaz come on than he was part of a swift move that ended with Greenwood’s deflected shot finally giving the hosts their second goal.
By this stage, Le Havre’s defence was all at sea a few minutes later, and Greenwood eased a defender off the ball as he fired home his hat-trick goal, shortly before, incredibly, adding his and Marseille’s fourth with a right-foot finish with 15 minutes to play.
Vaz soon tapped home Marseille’s fifth from two yards out, and though the final word seemed to belong to the visitors as Doucoure scored the goal of the game with a ferocious volley from outside the box in stoppage time, the hosts went straight down the other end, where Amir Murillo stooped to head home Marseille’s sixth.
Le Havre's loss brings their run of three successive draws to an end, and means that they've won just one of their opening eight league games (D3, L4).
Flashscore Man of the Match: Mason Greenwood (Marseille)