Lille moved to 70 points and will remain atop the table for another week at least, but defending champion PSG can close the gap to just a point if it defeats Saint Etienne on Sunday.
Andy Delort headed Montpellier ahead in the 21st minute on Saturday (AEST).
But Brazil's Luiz Araujo grabbed a deserved equaliser with five minutes left with a memorable half-volley.
The match was lengthened by seven minutes after Montpellier's Portuguese defender Pedro Mendes was seriously injured in a tussle for the ball with Lille's Jonathan Bamba.
The pair was chasing the ball as it headed towards touch, and Pedro Mendes's left knee appeared to go as he stretched for possession.
The 30-year-old was left screaming on the ground, and was taken from the field on a stretcher in tears.
He looks set to face several months on the sidelines if the injury turns out to be as serious as it seemed.