Second-placed Marseille surrendered their crown as they could only manage a 2-2 draw at home to Valenciennes.
The Coupe de France winners were involved in an enthralling game in the Parc des Princes. Ludovic Obraniak, whose goal clinched the cup, gave Lille the lead.
Guillaume Hoarau equalised for PSG before being sent off after receiving a second yellow. Ligue 1's leading scorer Moussa Sow restored Lille's advantage and though Mathieu Bodmer equalised against his former side, but a point proved enough to clinch the championship.
A 1-0 victory over Sochaux on Wednesday night was essentially the moment that les Dogues knew they would be crowned winners, as that pulled them six points clear of second-placed Marseille with only two games remaining.
Even if they had failed to pick up a point at the Parc des Princes, Marseilles would have needed to win both of their remaining matches to have any hope of overturning the deficit.
Since taking hold of top spot in November, Rudi Garcia’s side have only very briefly been deposed, with their ability to string together consistent runs of victories carrying them to a level above their competitors, who would frequently stumble.
The offensive players of Lille have caught most of the headlines, with the front three of Eden Hazard, Gervinho and Moussa Sow outstanding over the course of the campaign, but LOSC also have one of the best defensive records in France, testament to their all-round strength.
This is just their third title, with their previous championship coming in 1953-54, during what was previously considered to be the club’s Golden Age.