Mathieu Debuchy's strike 14 minutes from time saw Lille cut the gap on second-placed Montpellier.
Les Dogues' 1-0 victory at the Stade de Moustoir means they are now four points behind Montpellier HSC, who play Paris Saint-Germain at the Parc des Princes tomorrow.
Lorient tested Lille stopper Michael Landreau extensively in the first half, with the former French international pulling off three quality saves to keep the scores level.
The game's only goal came in the 74th-minute, when Debuchy managed to squeeze a shot past Benjamin Lecomte from an acute angle.
Alaixys Romao spurned a chance to snatch a point with the seconds ticking away, but Lille held firm and remain in the title hunt.
Defeat for Lorient means they drop two places into 13th, with Dijon and Brest moving above them into 10th and 11th respectively.
Lille play Rennes at home next week in what could prove to be a decisive match in the challenge for a Champions League spot.
Lorient will travel to Valenciennes, with both sides hoping to avenge defeat.
