PSG was already confirmed as champion earlier in the day after second-placed Lille could only draw 0-0 with Toulouse, and Thomas Tuchel's men subsequently played with freedom in an emphatic triumph inspired by Mbappe against his old club.
The lethal Mbappe took only 15 minutes to make his mark at the end of a stunning counter-attack and he doubled his tally just before half-time, rounding off another well-worked move.
Neymar, fit again after breaking his foot in January, came on after the interval to a huge cheer, before Mbappe completed his treble in the 55th minute to become the youngest player to score 30 goals in France's top division.
Aleksandr Golovin's late strike proved to be nothing more than a consolation for a Monaco side which still faces the threat of relegation.
Monaco's chances took an early blow when it lost goalkeeper Danijel Subasic to an apparent thigh strain, and PSG had the breakthrough soon after, Mbappe collecting Moussa Diaby's pass and finishing into the top-left corner to round off a devastating break.
The former Monaco talisman missed a great chance in the 33rd minute, but he made amends a few moments later, playing a one-two with Dani Alves and neatly finding the bottom-right corner from just inside the area.
PSG introduced Neymar for Layvin Kurzawa at half-time, but still Mbappe led the way, hitting the post after bursting past Kamil Glik in the 52nd minute.
He then grabbed his third, tapping in from close range after Alves raced on to Marco Verratti's pass and squared across the face of goal.
PSG lost Verratti to an injury towards the end and Golovin pulled one back with a tidy finish just inside the box, but the hosts' lead was unassailable and they cruised to victory.