The 19-year-old forward, fresh from helping France to World Cup glory over the summer, has made a devastating return to domestic action.
He was named on the bench by Thomas Tuchel for a trip to Guingamp on Saturday, but was to make a telling contribution in the tie.
Mbappe was introduced for the second half, with PSG surprisingly trailing at the interval.
Neymar restored parity with a 53rd-minute penalty, but the Brazilian was to be left in the shade by his exciting young team-mate.
With eight minutes left on the clock, Mbappe fired the reigning champions in front.
He then added his second and PSG’s third in stoppage-time, ensuring that a perfect start to the 2018-19 campaign is maintained by Tuchel’s side.
Mbappe’s efforts also saw him pass 30 goals in the French top-flight, with that landmark reached in a little over two seasons.
He opened his account for Monaco back in February 2016, before recording 15 efforts in a title-winning 2016-17 campaign.
Another 13 top-flight goals arrived last season and Mbappe is now up and running this term.
PSG will be looking to Mbappe for further inspiration over the coming weeks.
They have seen exciting U.S. starlet Timothy Weah – son of former World Player of the Year George – rise to prominence, but are currently without Edinson Cavani.
The Uruguayan striker is still nursing his way back from a calf injury picked up while away with his country at World Cup 2018.