PSG are in the process of trying to generate funds after breaking the world transfer record to sign Neymar from Barcelona, and while a fee has not been disclosed, it is believed that Juventus have paid £18.2m to sign the French international.
The 30-year-old has signed a three-year deal in Turin, and leaves Paris having scored 31 goals from 266 appearances in all competitions.
PSG chairman Nasser Al-Khelaifi said: "I will always have great memories of Blaise's six seasons with our club. He is a player who played every match with generosity and a permanent desire to win everything, earning admiration from everyone.
"Blaise will remain in our hearts and he will always be welcome in the big PSG family. We wish him every success in his first challenge abroad and every success with the France national team in this World Cup season."
Matuidi becomes the sixth first-team signing made by manager Massimiliano Allegri as the Italian looks to build a squad capable of building on their appearance in last season's Champions League final.