Marseille are amongst the favourites for the Championnat title, but they were second best against a determined Strasbourg side.
Corentin Martins opened the scoring on 20 minutes with a powerful header, but Marseille battled back with Didier Drogba denied an equaliser by the woodwork.
L'OM did haul themselves level shortly afterwards, with Steve Marlet capitalising on some slack defending to slot home.
Marseille were level for just four minutes as Mamadou Niang fired home a rebound after Vedran Runje failed to hold a Danijel Ljuboja shot.
The killer third goal came minutes into the second half as Ljuboja executed a fine finish to leave Runje stranded.
Marseille had chances to haul themselves back into the game, but were unable to find the target. This allowed Strasbourg to take their foot off the gas and they could even afford to go down to ten men after Christian Bassila was dismissed for fighting and also miss a penalty when Ljuboja saw his effort saved by Runje.
With Marseille chasing the game, Strasbourg capitalised on the space to score a late fourth through Fabrice Ehret.
Match summary
Strasbourg v Marseille
