Nolan Roux scored the goals in Lille's fully deserved 2-0 defeat of Monaco on Sunday which lifted the former French champions into second behind Paris Saint-Germain.
Roux's goals either side of the break extended Lille's run to seven games unbeaten and without conceding a goal and inflicted the first loss of the season on Monaco.
On paper this had looked a tough test for Lille against Claudio Ranieri's men who had begun the weekend level on points with table toppers PSG.
But Monaco found themselves returning home having slipped back into third, with Lille now on 26 points, two behind PSG who maintained their push for a second successive title with a 4-0 rout of Lorient on Friday.
Marko Basa celebrated his return from injury by playing an instrumental part in Lille's 27th minute opener, his header high over the Monaco defence being flicked in by Roux.
Monaco, led by Falcao, came out after the break with all guns blazing to try and find a way through Lille's stingy back line but the home side held firm, and in the 71st minute doubled their advantage.
On the counter attack former Chelsea striker Salomon Kalou raced down the centre, passing to captain Rio Mavuba who in turn found Roux who completed the move by knocking the ball in to an empty net.
Lille goalkeeper, Nigerian international Vincent Enyeama, performed double heroics right at the end when pushing away two quick-fire shots.
Earlier Bordeaux enjoyed a 2-1 win at Nice, while fourth-placed Nantes were held 1-1 at Montpellier.