Carlo Ancelotti's richly-assembled squad hung on for an invaluable 4-3 win, to go ahead of Montpellier on goals scored only, after they had been forced to battle back from 2-0 down.
Vincent Aboubakar and Remi Gomis stunned the capital club inside the opening 11 minutes but PSG's reply was even more impressive as they roared into a 3-2 lead before half-time.
Nene, Maxwell and Blaise Matuidi grabbed the goals and a defining win looked assured when Jeremy Menez added a fourth on 58 minutes.
But there was further drama as Aboubakar grabbed his second with 10 minutes left, but PSG just about managed to cling on for a win that puts the pressure back on Montpellier.
Montpellier can take over at the top outright again tomorrow night, although they face a tricky trip to fifth-placed Rennes.
Lyon's hopes of a top-three finish and Champions League football took a huge hit as drew 1-1 with relegation battlers Brest.
Yoann Gourcuff gave Les Gones a first-half lead, but Brest snatched a point through Gregory Lorenzi's equaliser.
The result leaves Lyon eight points behind third-placed Lille, who will assure themselves of a top-three finish if they beat Caen tomorrow.
Brest's point moved them out of the drop zone for 24 hours at least.
Ajaccio were plunged into relegation danger as they slipped to a 2-1 defeat at Evian and saw Carl Medjani red-carded late on.
The visitors took the lead through Benjamin Andre, but Cedric Barbosa immediately equalised and Daniel Wass' second-half free-kick earned the three points for Evian, who are set for a top-half finish in their first season following promotion to the top flight.
Ajaccio, by contrast, are just three points outside the relegation zone.
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