The Parisians had won all eight of its league games before traveling to mid-table Rennes but failed to register a single shot on target in the match, despite Lionel Messi, Kylian Mbappe and Neymar all playing from the start.
Rennes scored either side of halftime to cement a famous victory, with Gaetan Laborde and Flavian Tait getting on the scoresheet.
Despite dropping its first points of the season, PSG remains top of the table but the result does raise further questions about the balance within the team.
Mbappe, Messi and Neymar are rightly considered three of the best players on the planet and the three showed flashes of link-up play in the first half.
Messi, who scored his first goal for PSG Tuesday in the side’s impressive victory against Manchester City, came closest to scoring, but he instead saw his trademark free-kick smash the underside of the crossbar.
Despite some silky play, PSG failed to make the breakthrough, which allowed Rennes to strike twice to settle the tie.
Laborde arrived just in time to guide home a volley moments before the half-time whistle and Tait doubled the host’s lead with a sweeping finish after the restart.