PSG beat second-placed Marseille 3-1 on Sunday (Monday AEDT) to extend their lead at the top to 19 points with just eight rounds remaining.
The victory over their bitter rivals in the biggest game of French soccer came five days after PSG ousted Liverpool from the Champions League.
Still unbeaten in the league this season, PSG took the lead in the 17th minute. Ousmane Dembele ran behind the back of the defence after Khvicha Kvaratskhelia cleverly deflected the ball for Fabian Ruiz, who set up the France forward.
Dembele then skipped past Marseille goalkeeper Geronimo Rulli and scored his 21st league goal of the season in an open goal.
PSG made it 2-0 in the 42nd minute after Ruiz was expertly picked up by Achraf Hakimi and made the most of a lapse in the Marseille defence before crossing the ball for Nuno Mendes, who slotted the ball home.
Marseille pulled one back after the interval when a poor back pass was intercepted by Marseille captain Adrien Rabiot, who cut the ball back for Amine Gouiri to conclude the move.
Marseille's hopes of a comeback vanished for good in the 76th minute when Pol Lirola beat his own keeper as he tried to clear a dangerous cross from Hakimi.
The match between bottom side Montpellier and fellow strugglers Saint-Etienne was abandoned after a fire broke out in a stand due to flares thrown by home fans.
Montpellier were trailing 2-0 after Lucas Stassin scored twice for the visitors when the match was stopped by referee Francois Letexier.
Television footage showed black smoke coming from the fire. Players from both teams were sent back to their locker rooms and some Montpellier fans trashed seats in the stands. The fire was extinguished but the game did not start again for security reasons.
In a season marking the club's 50th anniversary, Montpellier sit rock bottom in the French league standings. Saint-Etienne are just one spot above in 17th place.
In other results, Lyon rallied past Le Havre 4-2, Brest and Reims drew 0-0, and Strasbourg beat Toulouse 2-1.
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