Mbappe converted a fourth-minute penalty, and netted the fourth goal just before the halftime break, as victory took PSG up to eight points from four games and into second spot, two behind leaders Monaco.
The spotkick was awarded after Manuel Ugarte was scythed down by home captain Corentin Tolisso and was followed by a second goal in the 20th minute from Achraf Hakimi after a one-two with Ousmane Dembele.
Marco Asensio made it 3-0 in the 38th minute before Mbappe showed PSG’s dominance with the fourth.
Tolisso netted a second-half consolation from the penalty spot for the home side, who have a single point from their opening four games with coach Laurent Blanc’s future looking uncertain.
(Writing by Mark Gleeson in Cape Town; Editing by Toby Davis)