Defending champions Marseille cut the lead at the top to three points with two games to play but Lille's goal difference is seven better than their rivals if they finish on the same number of points.
Marseille led through the in-form Loic Remy on 14 minutes before Lamine Kone's header from a corner and a goal from Ligue 1 joint-top scorer Kevin Gameiro put Europa League hopefuls Lorient in front.
Substitute and former Lorient striker Andre-Pierre Gignac grabbed a late equaliser for Didier Deschamps' side but it made little difference to the picture at the top.
The capitulation, the latest during Marseille's run-in, comes despite their vast experience compared to Lille.
A home victory on Wednesday will secure a first championship since 1954 for this term's surprise packages Lille, who won the French Cup on Saturday by beating Paris Saint-Germain.
Monaco thought they had won thanks to Benjamin Moukandjo's 14th minute goal but Raphael Varane struck in injury-time to send the principality side to third-from-bottom.
