Champions PSG are third on 26 points, behind Monaco, who destroyed Nancy 6-0 on Saturday, on goal difference, but three points behind Nice after the Azureans slumped to a 1-0 defeat at strugglers Caen.
PSG went ahead thanks to Gelson Fernandes's own goal and Cavani doubled the tally before the break, three minutes before limping off the pitch with an injury.
Adrien Rabiot and Marco Verratti scored the other two goals after the interval as PSG also hit the woodwork three times in an awe-inspiring display.
Benoit Costil deflected Cavani's header on to Fernandes, the ball bouncing off the midfielder into the goal after 31 minutes.
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Cavani made it 2-0 in the 42nd minute with a splendid 20-metre lob but was forced to leave the field with a thigh injury, being replaced by Jese after scoring his 11th goal in as many league appearances.
Rabiot put the result beyond doubt in the 67th minute with a long-range effort and Verratti rounded it off with a neat half-volley from inside the box from Hatem Ben Arfa's cross.
"We're getting where the coach wants us to go and it's paying off, everyone is motivated," said captain Thiago Silva, referring to Unai Emery, who took over from Laurent Blanc during the close season.
Nice had their first Ligue 1 defeat of the season as Ivan Santini's first-half penalty secured a 1-0 victory for strugglers Caen on Sunday.
Despite boasting considerable firepower up front with Alassane Plea, Younes Belhanda and Mario Balotelli, Nice were unusually toothless.
Three minutes before the break, Malang Sarr lost the ball to Ronny Rodelin, who sped into the area where he was brought down by Henrique Dalbert. Santini converted the resulting penalty by wrongfooting Nice keeper Yoan Cardinale.
Nice went close in the 63rd minute when Belhanda's through ball found Balotelli, only for the Italian's shot to crash against the post.
The visitors were more aggressive but Caen's defence held firm to help them escape the relegation zone as they moved up from 18th to 15th on 13 points.
(Editing by Clare Fallon)
