Marseille maintain perfect start
Jeremy Morel gave the home side a first-half lead and, although Julien Feret levelled for the visitors early in the second period, Andre-Pierre Gignac and a late own goal from Romain Danze secured the points.
The win ensured Elie Baup's side maintained their 100 per cent start to the season and moved two points clear of Lyon. Marseille came into the match having won three from three, including an impressive 1-0 triumph at Montpellier last weekend.
They made one change, with Kassim Abdallah coming in for Stephane M'Bia, who moved to Queens Park Rangers on Friday, as both Rod Fanni and Gignac recovered from minor knocks to start at the Stade Velodrome.
Rennes had registered one win and two defeats from their opening three, with victory coming last week against Bastia. They also made one change as Sadio Diallo dropped to the bench, with Vincent Pajot taking his place in the middle of midfield.
Morel puts Marseille in front
Marseille, watched by new signing Joey Barton, were quicker out of the blocks as Gignac shot over from close range after three minutes and seconds later Andre Ayew headed wide from an Abdallah cross.
Mathieu Valbuena had the first effort on target, forcing Benoit Costil to tip over after 15 minutes before Morgan Amalfitano and Fanni both went close. Their dominance finally led to a goal ten minutes before the break as Morel's left-footed shot from the edge of the area beat Costil.
Rennes equalised in the 57th minute with their second shot on target thanks to Feret, who powered into the roof of the net from the corner of the box.
Marseille were finding chances a lot more difficult to come by in the second period than they were in the first, and it took until the 80th minute for them to test Costil in the second half, with Gignac's right-footed effort forcing the stopper to tip wide.
However, Gignac was to find the net just two minutes later as he found the bottom right hand corner from the edge of the area. Ayew had a golden chance to make it three with just two minutes remaining, but headed over from ten yards out, before Danze's own goal in stoppage time sealed his side's fate.