Lionel Messi Dreams of Champions League Win at Star Studded Paris St-Germain
The Argentina captain, 34, won four Champions League titles with Barcelona, the last of which came in 2015.
PSG are still searching for their first title in the competition, having lost to Bayern Munich in the 2020 final.
"My goal and my dream is to win the Champions League once more," Messi said as he was unveiled as a PSG player.
Messi left Barcelona - who he joined aged 13 - as they were unable to afford a new deal under La Liga's financial fair play rules. Considered one of the greatest players of all time, he scored a record 672 goals in 778 games for the Catalan giants.
He won the Ballon d'Or a record six times and lifted 35 trophies during his time at the Nou Camp, but said he is excited to "begin this new moment of my life" after a "difficult" departure from Barcelona.
"It was a difficult change after so long a time," he told reporters at the Parc des Princes. "But the moment I arrived here, I felt very happy and I really want to begin the training sessions. I want it to be quick.
"My only will now is to begin the training sessions. I want to work with the staff and team-mates and begin this new moment of my life.
"I have this will to play. I am really impatient. I still want to win, as I did the first moment of my career.
"I feel this club is ready to fight for all the trophies. This is my goal, I want to keep growing and keep winning titles and that is why I came to this club."