The Italian has established himself as the French champions' number one, playing 37 of 38 matches as Laurent Blanc's men lifted the Ligue 1 title for the second season in a row last term.
And Sirigu, who has been with the club since joining from Palermo in 2011, believes PSG have only scratched the surface when it comes to the team's potential.
"I wanted to continue this incredible adventure, both on a sporting and on a human level, with Paris Saint-Germain," he said.
"I know we are only at the start of something exceptional.
"We are going to win a lot of titles together."
President Nasser Al-Khelaifi added that the 27-year-old is an integral part of the squad at PSG.
"We are very proud to extend the contract of Salvatore, an exceptional goalkeeper and a remarkable human being," he proclaimed.
"He is a symbol of the Paris Saint-Germain project: to build one of the most successful clubs in Europe."
PSG travel to Rennes in the French top flight on Saturday.