Media reports said Chevalier has joined PSG for a fee of around 40 million euros ($47 million), with the 23-year-old in line to succeed Italy keeper Gianluigi Donnarumma, who has a year left in his contract with the Paris-based club, as the number one custodian in Luis Enrique's team.
"I am a kid that is living his dream. Ever since I was small I wanted to play at the very highest level," Chevalier said in a statement.
"I'm really delighted to be here. I will wear this shirt with passion and ambition."
Calais-born Chevalier graduated from Lille's youth academy and played on loan for Valenciennes before becoming the first-choice keeper at his parent club during the 2022-23 season.
He was named Ligue 1's goalkeeper of the year for the 2024-25 season by the UNFP trade union for professional footballers in France.
"Lucas is one of the leading goalkeepers in France and Europe and a fantastic addition to our team - as we continue to build everything for the long-term based on the collective," said PSG President Nasser Al-Khelaifi.
Ligue 1 and Champions League winners PSG face Tottenham Hotspur for the UEFA Super Cup on Wednesday.