Rennes completed a league double over the runaway leaders, Paris St-Germain, who suffered their first Ligue 1 home defeat since April 2021.
Karl Toko Ekambi scored for the visitors just before half-time, and Lesley Ugochukwu broke down the left and squared the ball for former PSG forward Arnaud Kalimuendo to add the second three minutes after the break.
PSG’s unbeaten league run at the Parc des Princes came to an end after 35 games. Despite the defeat, Christophe Galtier’s side remains nine points clear of Lens at the top of the table, edging closer to their 11th title in 13 years.
Meanwhile, Rennes became only the third team to complete a league double over PSG since Qatar Sports Investments acquired the club in 2011. Rennes currently sit in fifth place, four points behind Monaco in fourth but only three points away from second-placed Lens.