Lille defender Aurelien Chedjou's second-half own goal earned Carlo Ancelotti's men their ninth win in 10 games and lifted them back above Lyon on goal difference.
Referee Freddy Fautrel also controversially ruled out a first-half goal for the visitors, who were left languishing in mid-table.
One goal was also all that was required for in-form Bordeaux to beat Nice and leap-frog their hosts into fifth place.
Henri Saivet's second-half strike earned Bordeaux, who have lost just one of their last eight league matches, their first victory at the Stade du Ray since 2005 and consigned Nice to only their second defeat in 12 outings.
In Sunday's other match St Etienne boosted their hopes of European football next season with a 3-0 victory over Bastia at the Stade Geoffroy-Guichard.
Brandao opened the scoring after nine minutes and further goals in the final 11 minutes from Pierre-Emerick Aubameyang and Josua Guilavogui sealed Les Verts' first home league win since November.
The result - a repeat scoreline from the reverse fixture earlier in the campaign - leaves St Etienne in seventh spot, a point behind Nice and Bordeaux.