Mbappe took his league tally for the season to 30 following his treble, which came just hours after PSG were crowned champions for the sixth time in seven years when closest challengers Lille dropped points.
Neymar's return at the start of the second half replacing Layvin Kurzawa is the cherry on the cake for Thomas Tuchel's side, who had been without the Brazilian superstar since January 23 with a right foot injury.
Edinson Cavani also returned to action as a second half substitute, having a late strike correctly ruled out for offside, meaning that PSG's famed front three are back together following months apart.
Mbappe has thrived in the absence of his strike partners, and gave his side a 2-0 first-half lead with two neat finishes, the first coming in the 15th minute and the second seven minutes before the break after a beautiful pass from Dani Alves.
The World Cup winner then put the three points beyond doubt when he tapped in Alves' low cross nine minutes after the break.
Aleksandr Golovin rolled home a consolation for the away side, who remain in trouble in 16th place and are only four points away from the relegation play-off spot.
On Sunday afternoon Lille ended their challenge with a goalless draw at Toulouse that left them 16 points behind PSG with only five games to play and allowed capital club to celebrate the title after missing chances to seal it in their previous matches.
The Parisians have struggled with key injuries in recent weeks and they lost Italian international midfielder Marco Verratti with what looks like a knock to his left ankle.
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