Nantes swapped places with Marseille after a goal by Alejandro Bedoya gave them a 1-0 win over OM in Ligue 1.
Bedoya slotted a right-footed shot home after 16 minutes to give Nantes victory at the Stade Velodrome, also inflicting a second successive defeat on their hosts.
It saw Nantes leapfrog their OM into fourth in the table, one place and two points above them.
Bedoya's goal came after little more than a quarter of an hour from the first real attack of the match.
Vincent Bessat released Filip Djordjevic in the area and he flicked the ball toward Bedoya, who finished neatly just inside the post.
Marseille responded with a 25-yard shot by Dimitri Payet which Remy Riou in the Nantes goal repelled.
Nantes then came close when Bedoya found Bessat 25 yards out and his shot went inches wide.
The visitors came close eight minutes after the break when Djordjevic freed Serge Gakpe on the right of the area and he curled a right-footed shot effort which missed the top corner by inches.
Riou came to Nantes' rescue when he parried Saber Khelifa's snapshot only for the ball to go to Dimitri Payet, but the keeper also pushed his shot away.
The visitors were once again indebted to Riou when Khelifa found Thauvin at the top of the area with the keeper repelling his low right-footed drive.
It was then Steve Mandanda's turn to impress in the Marseille goal as he thwarted Djordjevic when the striker had a one-on-one.