Lille was on the brink of its first Ligue 1 title since 1954 as it opened a seven-point gap with a 2-1 win at St. Etienne on Tuesday.
The northerners recovered from a shaky start to prevail with goals by Tulio de Melo and Rio Mavuba and now have 69 points with three games left. Second-placed and champion Olympique Marseille will play its game in hand at home against Stade Brest.
Paris St. Germain's hopes of securing a qualifying spot for the Champions League third qualifying round took a knock when it was held to a 2-2 home draw by relegation-threatened Nancy that left it in fourth place, one point adrift of Olympique Lyon.
At St. Etienne's Geoffroy Guichard stadium, the Lille defense was caught snoozing early on as Laurent Battles collected a through ball, stumbled on Mickael Landreau but Emmanuel Riviere, who had followed, poked the ball into an empty net to make it 1-0 after six minutes.
The visitors reacted swiftly and Tulio de Melo levelled with a delicate volley from the spot from an Eden Hazard cross in the 14th minute.
St. Etienne was awarded a penalty after the referee harshly ruled that Riviere had been fouled by two Lille defenders but Landreau parried away Bakary Sako's attempt on 18 minutes.
Lille increased the pressure after the break and was rewarded in the 66th minute when midfielder Rio Mavuba unleashed a fierce 30-meter shot that beat Jeremy Janot after taking a slight deflection off Sylvain Monsoreau.
"We have a goal and we're trying to do everything we can to reach it," Mavuba told French TV. "(After St. Etienne opened the scoring) we kept our cool, we just tried to play some good football and did what we had to do."