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.
Reims, managed by Belgian-born Englishman Will Still, took the lead through Arsenal loanee Folarin Balogun in the 13th minute.
But two first-half goals from Alexis Sanchez gave Marseille a 2-1 win with Balogun striking the post in second-half injury time.
Christophe Galtier's PSG side are seven points clear of Marseille at the top of the table as they head towards an 11th title in 13 years.
Meanwhile, Rennes - who are just the third side to get the double over Paris St-Germain since Qatar Sports Investments bought the club in 2011 - sit fifth, four points off Monaco in fourth and seven off third-placed Lens.