The Italian goalkeeper played a pivotal role as PSG won their first Champions League title last season as the French club captured a historic treble.
The 26-year-old has now been left out in the cold, with the shot-stopper having one-year left on his current contract.
"Unfortunately, someone has decided that I can no longer be part of the group and contribute to the team's success," Donnarumma posted on social media on Tuesday.
"I am disappointed and disheartened."
He added: "I hope to have the opportunity to look the fans at the Parc des Princes in the eyes one more time and say goodbye as it should be done.
"If that doesn't happen, I want you to know that your support and affection mean the world to me and I will never forget it.
"Playing for this club and living in this city has been an immense honour. Thank you Paris."
Donnarumma is now set to move on, especially since PSG have signed French keeper Lucas Chevalier.
PSG manager Luis Enrique said: "These are always hard decisions to make. I can only say good things about Gianluigi Donnarumma.
"He is one of the best players in his position, without any doubt. He is even better as a person, but we were looking for a different profile of keeper.
"Bearing in mind the level of Gianluigi Donnarumma and everything he has given to the club, of course we understand the situation but my aim is to improve the team and I have tried to do that in the best way possible."
In a thrilling UEFA Super Cup clash in Udine, Paris Saint-Germain overcame a 2-0 deficit to defeat Tottenham Hotspur 4-3 on penalties after a 2-2 draw, claiming their first Super Cup title and fifth trophy of 2025.
Yves Bissouma has been left out of the Tottenham squad to face Paris Saint-Germain in the UEFA Super Cup on Wednesday night.
Luis Enrique has revealed he turned down the chance to manage Tottenham Hotspur in 2023, a decision that has shaped the narrative for this week's UEFA Super Cup.
Paris Saint-Germain have secured the signing of defender Illia Zabarnyi from Bournemouth, adding one of the Premier League's most reliable defenders to their ranks.
