Souleymane Camara missed a penalty kick nine minutes into stoppage time, ending a wild finish where four players were sent off in stoppage time of a 2-2 draw against Evian on Tuesday.
Olivier Giroud had his Ligue 1-high 21st goal in the 84th minute, as the hosts responded late to consecutive goals from Evian that erased a first-half lead.
With the game drawing to a close, Cedric Cambon fouled Remy Cabella in the box deep in stoppage time and Evian's Cedric Mongongu and Saber Khelifa as well as Montpellier's Younes Belhanda and Gregory Lacombe were sent off.
After the long delay, Camara - who set up Giroud's goal - had his penalty kick saved by Evian goalie Stephan Andersen on the final kick of the match.
Belhanda gave Montpellier its only lead in the 42nd minute from the spot, but Thomas Kahlenberg and Kevin Berigaud scored on each side of half to take the leaders to the limit.
Montpellier had won five of its last six matches, and wasted a chance to move eight points clear of PSG atop the standings. Montpellier instead leads by six with its title rival still to play Wednesday against St. Etienne.
Evian had won three of its last four, but remained in ninth on 46 points ahead of Wednesday's matches.