James Fanchone's late winner saw Lorient keep themselves in the race for European football as Grenoble slid further towards the Ligue 1 trap door at Stade des Alpes.
Grenoble are adrift at the bottom of the table and now lie 17 points from safety with just seven games left to play but they took an early lead through Nassim Akrour.
Kevin Gameiro levelled for Lorient in the first half before Fanchone's late winner.
The home side had won only three of their 30 league games heading into tonight's clash, but they gave themselves the best chance of securing a fourth by taking the lead with three minutes on the clock.
Daisuke Matsui made an overlapping run on the left and his excellent cross allowed Akrour to lob his header over Lorient goalkeeper Fabien Audard.
And Akrour should have doubled the lead in the 16th minute as Daniel Ljubola slipped the ball to the forward 12 yards out, but he managed to miss the target.
Gameiro had a chance to equalise on the half-hour mark but could not beat Brice Maubleu in the Grenoble goal. But he made no mistake two minutes later when Morgan Amalfitano played him in and he lobbed the ball into the net.
Grenoble's best chances continued to fall to Akrour but he was denied twice by Audard after a delicate flick by Laurent Courtois had played him in on goal.
The Algeria forward then headed against the post as he was picked out by Matsui's free-kick.
Lorient regrouped and went in search of a winner with Fanchone crossing for Amalfitano to fire in a powerful shot that Maubleu did well to beat away.
Akrour had yet another chance for the hosts but Audard produced a fingertip save to deflect his header over the bar.
And Grenoble were made to pay for their profligacy when Pierre Ducasse found Fanchone in space and the former Le Mans midfielder drove into the box to fire underneath Maubleu into the bottom corner.