Paris St-Germain fell to their first Ligue 1 home defeat since April 2021 as Rennes completed a league double over the runaway leaders.
The visitors scored either side of half-time with Karl Toko Ekambi firing them in front before Arnaud Kalimuendo added a second three minutes after the break.
PSG saw their unbeaten league run at the Parc des Princes ended at 35 games.
Reims also saw their 19-match unbeaten run stopped by defeat to Marseille.
They had last lost a league match in September in a 3-0 loss to Monaco.
The visitors scored either side of half-time with Karl Toko Ekambi firing them in front before Arnaud Kalimuendo added a second three minutes after the break.
PSG saw their unbeaten league run at the Parc des Princes ended at 35 games.
Reims also saw their 19-match unbeaten run stopped by defeat to Marseille.
They had last lost a league match in September in a 3-0 loss to Monaco.