Lille were attempting to win a sixth away match in succession and were the first side to threaten 15 minutes in when Thomas Meunier played Ayyoub Bouaddi in behind the defence on the left, but Lukas Hradecky covered his near post well to make the save.
The visitors thought they had the perfect chance just two minutes later when referee Clement Turpin awarded a penalty after Matias Fernandez-Pardo went down under Jordan Teze’s challenge, but following a VAR review, the decision to award the spot-kick was overturned.
Following that let-off, the home side began to enjoy more of the ball, but other than a Maghnes Akliouche volley in the 27th minute that bobbled towards Berke Ozer, they failed to create opportunities.
Les Dogues proceeded to give Monaco a helping hand late in the half, giving possession away cheaply in their third of the pitch, which allowed Teze and Akliouche to link up, only for the latter to pull his shot across goal.
Both sides kept pushing to take a precious lead into half-time, but Fernandez-Pardo failed to make contact with Hakon Haraldsson’s ball across goal, then Simon Adingra saw his effort fly over Ozer’s crossbar.
Monaco’s previous six matches had seen both teams score, but after Felix Correia planted an effort over the bar and Meunier fired another straight at Hradecky, the hour mark came with the deadlock unbroken.
Akliouche continued to be Les Monégasques’ danger man in attack, sending a stinging drive on target, but Ozer was right behind it.
However, with 18 minutes to play, the long journey south looked to be a fruitful one for Lille, as Gaetan Perrin got free on the left and squared for Meunier, and in his attempts to prevent a simple finish for the Belgian, Denis Zakaria slid in and turned the ball into his own net.
In response, Sebastien Pocognoli’s team didn’t do enough to test Ozer late on, as Lille attempted to kill the game off on the break with chances for Ethan Mbappe and Fernandez-Pardo, but one goal was enough in the end.
It’s just a second league defeat in 15 for a Monaco side that had scored at least twice in 12 of their previous 13 competitive outings.
Bruno Genesio’s side, meanwhile, are 13 league games unbeaten and climbed into the top three with this win, but Rennes’ victory this evening means they are still just two points clear of fifth heading into the final day.
Flashscore Man of the Match: Thomas Meunier (Lille)