Saint-Etienne will play in Europe next season after beating Montpellier 2-0, and they are all but certain of direct qualification via fourth place in Ligue 1 having seen Marseille beat Lyon 4-2 in the evening kick-off.
Goals by Romain Hamouma and Mevlut Erding early in the second half proved sufficient for Saint-Etienne to move five points clear of Lyon, who could do nothing to close the gap later in the day.
Defeat for Montpellier means they are still not completely safe from relegation, although with 42 points the 2012 champions should have enough in the bank to stay up.
OM won with the help of a brace from Andre-Pierre Gignac.
The hosts raced into a two-goal lead inside half an hour, courtesy of Souleymane Diawara and Florian Thauvin, before Arnold Mvuemba pulled one back before half-time.
After the break Marseille turned the screw as Gignac took his tally to 16 for the season before Bafetimbi Gomis notched a second consolation for the visitors.
The result leaves Marseille only two points behind Lyon in the battle for fifth, which comes with a place in the Europa League qualifiers after Paris St Germain's Coupe de la Ligue triumph.
Sochaux gave themselves a chance of escaping relegation with a third win in four games, beating 10-man Nice 2-0.
Twelve points from six unbeaten matches has lifted them to within a point of safety and their home game against Evian, immediately above them, on the final day of the season in a fortnight looks like being the decider.
Jordan Ayew had a hand in both his side's goals; his run and cross forced defender Nemanja Pejcinovic to turn the ball into his own net before half-time and the Ghanaian headed in a second after the break.
Evian are only a point clear of Sochaux after slipping to a 1-0 loss at Reims.
Prince Oniangue fired Reims in front after half an hour, while Cedric Mongongu missed a glorious chance to level for the visitors from the penalty spot four minutes from time.
Julien Faubert confirmed Valenciennes' relegation after his late goal secured a 1-0 win for Bordeaux at the Stade du Hainaut.
Going into the game the hosts - present in the top flight since 2006 - knew they needed a miracle to pull themselves out of trouble given their inferior goal difference, but Sunday's result secured their fate.
To make matters worse for VA, they missed a golden chance to score early on as Maor Melikson's penalty was saved by Bordeaux goalkeeper Cedric Carrasso.
Toulouse's search for a Ligue 1 win continues after they were held 1-1 at home by a Nantes side who finished the match with 10 men.
It is now seven matches since Toulouse last tasted victory, and while there is clearly no sign of panic from a club who handed coach Alain Casanova a new contract this week, it is no doubt a concerning run as they headed into the summer.
They were on the back foot early on in this one as Oswaldo Vizcarrondo headed home Olivier Veigneau's ninth-minute free-kick, but levelled through Wissam Ben Yedder in the 67th minute.
A red card for Nantes' Papy Mison Djilobodji, who clashed with Ben Yedder after his goal, opened the door for Toulouse but they could not push through with Mihai Roman's spectacular overhead kick coming back off the crossbar 11 minutes from time.
There was the all-too-familiar taste of defeat for Ajaccio, who missed a penalty in losing 1-0 to Lorient.
Jeremie Aliadiere put Lorient in front and, although Ecuele Manga was then controversially sent off for bringing down Paul Lasne five minutes later, Aboubacar Camara saw his spot-kick saved by Fabien Audard.