Substitute Salomon Kalou scored a stoppage-time winner to seal a 1-0 win for Lille at the Stade Pierre-Mauroy that broke the hearts of visiting Guingamp.
With the game seemingly petering out towards a goalless draw, the former Chelsea man came off the bench to hammer home his 11th goal of the season and inflict a second straight Ligue 1 defeat on Jocelyn Gourvennec's men.
For large parts of the match, the hosts seemed the more likely to break the deadlock, but for an inspired display from Vincent Enyeama, and in the end Lille secured the win which moved them within six points of second-placed Monaco.
St Etienne kept up the pressure on third-placed Lille with an impressive 2-1 win in the Rhone Valley derby at Lyon.
Mevlut Erding set the hosts on their way to a first win in eight against their neighbours with his third goal in two matches but that lead was short lived thanks to an Alexandre Lacazette leveller.
However, substitute Max Gradel ensured Les Verts remain just three points behind Lille with his first goal this year.
Rennes won back-to-back league games for the first time this season with a comfortable 3-0 win over out-of-form Bastia.
Romain Alessandrini set the hosts on their way with his fifth goal of the season on 14 minutes before Ola Toivonen added a second to tee up a ninth win this term for the Brittany side.
Jean Makoun's first strike of the season just after the break completed a miserable afternoon for Frederic Hantz's side who have now won just once in their past seven outings.