France winger Thauvin missed most of last season with an ankle injury but his close-range volley on 31 minutes at the Parc des Princes earned Marseille a first victory over its bitter rival since November 2011.
PSG, which lost the Champions League final to Bayern Munich last month, has now lost its opening two games of a season without scoring for the first time since 1978/79 and the task for Thomas Tuchel’s coronavirus-afflicted side does not get any easier this month.
A frenzied schedule awaits, starting with the visit of Metz in midweek and a trip to Nice next Sunday, and Neymar now faces a suspension for a slap on Marseille defender Alvaro Gonzalez in an injury-time scuffle that resulted in five red cards.
The Brazilian appeared to accuse his opponent of racism as he followed Layvin Kurzawa and Leandro Paredes down the tunnel after he was sent off following a VAR review.
Argentine striker Dario Benedetto and left-back Jordan Amavi were shown red cards for the visitor.
Marseille is attempting to close the gap on PSG after coming a distant second last season and finds itself with an early six-point advantage over a club that has won the title seven of the past eight years.
RESULT: PSG 0 lost to Marseille 1 (Thauvin 31)