In Brest, Mbappe returned from a one-match ban and fired PSG ahead on nine minutes, running from just inside the halfway line and drilling a left-footed shot into the top corner from the edge of the area. Julian Draxler set up Pablo Sarabia for a second goal before half-time, the Spaniard sweeping home for the second game in a row having hit the winner against Bordeaux in midweek.
Angel Di Maria came off the bench for his first appearance in a month following a thigh injury, a timely boost alongside the return of Marco Verratti ahead of next week's second leg against Barcelona in the Champions League last 16. Verratti created PSG's third, somewhat inadvertently, as he prodded across goal and straight into the chest of Mbappe, wrong-footing Brest goalkeeper Sebastien Cibois.
Seventeen-year-old Rayan Cherki scored twice for Lyon as they overcame a spirited effort from Ligue 2 side Sochaux, winners of the competition in 2007. Algerian defender Djamel Benlamri headed Lyon ahead at home before Maxwel Cornet volleyed in a second to put the hosts in control.
Chris Bedia pulled a goal back for Sochaux only for Cherki to restore Lyon's two-goal cushion before half-time with a crisp low finish. Bedia's second of the game again gave Sochaux hope but Jason Denayer nodded in from a corner and Cherki completed the victory three minutes from time.
Also on Saturday, fourth-tier Le Puy beat Ligue 1 strugglers Lorient 1-0. Lenny Joseph outpaced the visiting defence to finish off a 61st minute counter-attack and give Le Puy, who play in National 2, victory over Lorient, who are 17th in the top division.
Metz won 4-0 at second-division Valenciennes, while Montpellier shook off fifth-tier Ales 2-1.
Standout matches today