Lille equalized five minutes into stoppage time to deny leaders Paris St-Germain a ninth successive Ligue 1 win.
Kylian Mbappe converted a penalty as PSG looked to be heading seven points clear at the top of the table. But substitute Jonathan David headed in from close range after goalkeeper Arnau Tenas blocked Adam Ounas’ effort.
PSG are on 37 points as they chase a 10th French title in 12 seasons, with second-placed Nice five points back. Monaco sit third with 30 points.
Despite Sunday evening’s disappointment, Luis Enrique’s PSG ended the weekend in a stronger position than they began it. Monaco were beaten 1-0 by Lyon on Friday before Nice fell to a 3-1 loss at Le Havre on Saturday.