PSG announced late on Thursday the Brazilian striker had signed a five-year contract with the French club.
After completing his blockbuster transfer to PSG from Barcelona, Neymar is now the most expensive player in football history.
His release clause (€222 million, or $263 million) was worth more than double that paid for French midfielder Paul Pogba who moved from Juventus to Manchester United last summer.
Speaking at a news conference at the Parc des Princes stadium in Paris, PSG President Nasser al-Khelaifi welcomed the player to his "new home" and said that, for him, Neymar was "the best player in the world".
"Neymar is an idol for the whole world," al-Khelaifi said.
"He’s brought so many positive things already. Our fans have always dreamed about having Neymar, and here he is today. Ligue 1 [French football league] is getting more competitive, and Neymar has signed to win all the trophies we can. We want to win all the trophies we can. Thank you Neymar for coming to PSG, thanks to your family and your staff, and to my staff who worked really hard on this transfer," he added.
Al-Khelaifi also revealed that it was PSG, not Neymar himself, that paid the former Barcelona player's release clause.
Neymar thanked al-Khelaifi for the "new challenge, at PSG, in this wonderful city."
"I really can’t describe what I’m feeling in my heart. I’m really looking forward to getting started, and to achieve what I want to achieve," he said. "I wanted a bigger challenge, and my heart made this decision and I followed my heart. I want to help this club succeed and win trophies."
Neymar said it was "the most difficult decision" of his life to leave Barcelona and join PSG.
PSG midfielder Javier Pastore has relinquished the No.10 jersey to Neymar as a "sign of welcome".
Thousands of PSG fans have stood in line since the early morning hours in front of the club's stores in Paris to purchase the jersey of the player.
"Neymar Jr is now committed to the French capital’s club until June 30, 2022," PSG announced in a statement on Thursday.
"At 25 years old, he has already been selected for the Brazilian national team 77 times, scoring 52 goals," the club added.
"As captain of the national team, Neymar da Silva Santos Junior has emerged as the leader of a team aiming to win its sixth World Cup in 2018. Wearing the Brazil jersey, Neymar Jr has already carried his country to its first Olympic title at the Rio Games in 2016."
The statement also quoted Neymar as saying: "'I am extremely happy to join Paris Saint-Germain'."