Rene Girard's men, who had won just two of their previous nine Ligue 1 matches, recorded a 2-0 victory over Montpellier and now hold a four-point advantage over fourth-placed Saint-Etienne, who went down 1-0 at Lorient.
Goals in either half from Marko Basa and Nolan Roux made the difference for Lille at Stade Pierre-Mauroy against their coach's former club.
Basa headed home from Florent Balmont's 18th-minute free-kick and Roux doubled the hosts' advantage 12 minutes into the second half with an acrobatic volley after David Rozehnal had struck the crossbar.
If Lille were content at securing three points, a further boost was not long in coming as their nearest rivals in the race for third failed to follow suit.
Saint-Etienne enjoyed the better of the first half at Lorient, but were unable to make a breakthrough.
The hosts hit the post through Vincent Aboubakar before grabbing a dramatic 90th-minute winner from the penalty spot.
Josuha Guilavogui handled inside the penalty area and Jeremie Aliadiere maintained his composure to convert from 12 yards, securing Lorient's second win of the year.
There was even more late drama at Stade Jacques Chaban-Delmas as Lyon grabbed two injury-time goals to earn a sensational 2-1 success against fellow European hopefuls Bordeaux.
Henri Saivet's seventh-minute strike gave Bordeaux the lead and looked set to lift Francis Gillot's men above their opponents.
Yet Lyon turned things around in dramatic fashion, with Henri Bedimo levelling in the 91st minute before teenager Corentin Tolisso popped up with an unlikely winner on only his second Ligue 1 start.
Lyon now sit just three points behind Saint-Etienne, with both sides facing stiff tests next Sunday against Monaco and Paris Saint-Germain respectively.
