The 2008 Uefa Intertoto Cup champions Rennes ended Paris St-Germain’s 100% start in Ligue 1 as Lionel Messi suffered his first defeat since arriving at the club.
The hosts scored two quick goals either side of half-time through former French national youth team Gatetan Laborde and Flavien Tait.
Mauricio Pochettino’s side did not have a single shot on target, despite Messi, Neymar and Kylian Mbappe all starting.
The defeat is PSG’s first in Ligue 1 since April, when they were beaten by last season’s eventual champions Lille.
The result leaves PSG top of Ligue 1 on 24 points, six points clear of Lens, while Rennes move up to seventh.