Barcelona announced earlier today that the 25-year-old's representatives had triggered his €222m (£198m) release clause in order to allow him to leave the club and join the Ligue 1 outfit.
It has been claimed that Neymar will be reimbursed as part of a €300m (£271.3m) deal from PSG's Qatari owners to make the Brazilian an ambassador for the 2022 World Cup.
Neymar has put pen to paper on a five-year deal at the Parc des Princes, keeping him at the club until June 30, 2022.
"I am extremely happy to join Paris Saint-Germain. Since I arrived in Europe, the club has always been one of the most competitive and most ambitious," Neymar told the club's official website.
"And the biggest challenge, what most motivated me to join my new teammates is to help the club to conquer the titles that their fans want. Paris Saint-Germain's ambition attracted me to the club, along with the passion and the energy this brings.
"I played four seasons in Europe and I feel ready to take the challenge. From today, I will do everything I can to help my new teammates, to open up new horizons for my club and to bring happiness to its millions of supporters around the world."
PSG president Nasser Al-Khelaifi added: "It is with immense joy and pride that we welcome Neymar Jr to Paris Saint-Germain. Neymar Jr is today one of the very best players in world football.
"His winning mentality, strength of character and sense of leadership have made him into a great player. He will bring a very positive energy to this club. In six years, we have built a very ambitious project that has already taken us to the highest level of national and European football. Today, with the arrival of Neymar Jr, I am convinced that we will come even closer, with the support of our faithful fans, to realizing our greatest dreams."
Neymar, who will wear the number 10 shirt in the French capital, leaves Barcelona having scored 105 goals in 186 appearances during his four years at the club, helping them to eight trophies including two league titles and the 2015 Champions League.
The deal obliterates the old transfer record of £89m, which was spent by Manchester United to bring Paul Pogba back to Old Trafford last summer.