Strasbourg 2 - 1 PSG
PSG shocked by Strasbourg and lose first game of season
Mbappé levelled things up after Da Costa's opener, but a goal from Bahoken confirmed the doubts that have been raised about certain aspects of their game.
Paris St Germain suffered their first defeat of the season in any competition with Strasbourg ending the runaway leaders' aura of invincibility in Ligue 1 with a 2-1 victory at the Stade de la Meinau on Saturday.
PSG stars not invincible
PSG, who had been expected to stretch their 10-point lead with some comfort at a club starting the day in 17th place, were on the end of a major shock as a 65th-minute goal from Stephane Bahoken ended their season-long, 15-match unbeaten league sequence.
Strasbourg had gone ahead through Nuno Da Costa after 13 minutes but normal service seemed to have been resumed when Kylian Mbappe equalised soon before halftime.
Despite having to soak up huge pressure after Bahoken again gave Strasbourg the lead, the newly-promoted side survived the onslaught for a famous win, the first by any side over PSG in either domestic or European competition in 2016-17.
Hope for Monaco and Lyon
The defeat gives PSG's distant pursuers fresh hope with Monaco aiming to narrow the gap to nine points in one of Saturday's later games at home to Angers while Olympique Marseille can get to within seven points by winning at Montpellier on Sunday.