The 34-year-old completed his move to the Parisians on a free transfer on Wednesday, telling the club's supporters he is "ready to fight for all the trophies" on offer.
The thought of seeing Messi line up alongside the world's two most expensive players - Neymar and Kylian Mbappe - is a mouthwatering one, so when might we see Messi in a PSG shirt?
When is Messi's first PSG match?
PSG fans are likely to have to wait a few weeks before they see the Argentina forward in action on the pitch.
Mauricio Pochettino’s side host Strasbourg in their second Ligue 1 fixture of the new season on Saturday but it is unlikely Messi will be ready to play after having a month off after Argentina’s Copa America win.
PSG travel to Brest on August 20, but even that could come too soon. A more realistic target for Messi's PSG debut would appear to be the away trip to Reims on August 29.
Why do PSG fans need to wait so long?
Messi's future has been the subject of some conjecture since the end of last season.
He played at this summer's Copa America - Messi was instrumental as Argentina beat hosts Brazil in the final - while negotiating with Barcelona over a new long-term deal after his contract had expired, making him a free agent.
Asked about his PSG debut at his official presentation on Wednesday, Messi said: "I was on holidays and it’s very new. I spoke yesterday with the technical staff, so, maybe I need a pre-season.
“I’m going to begin to train and work and I hope I can play as soon as I can, when the staff thinks I’m OK, I’ll be ready.”
Why did Messi leave Barcelona?
Messi had agreed to stay at Barcelona for five more years, but even with a 50 per cent pay cut Barca would have fallen foul of Spain's financial rules by keeping him.
Both parties confirmed his departure on Saturday and the following day Messi held an emotional press conference in which he explained his departure, saying he had done "all he could to try and stay".
"The truth is don't know what to say," Messi said, fighting back tears. "In recent days I have given lots of thought to what I can say and the truth is that I can't think of anything.
"This is really difficult for me after so many years being here, my entire life. I'm not ready for this.
"After 21 years I'm leaving with my three Catalan Argentine kids. We've lived in this city, this is our home. I'm just really grateful for everything, all my teammates, everyone who has been by my side."
Messi's contract at PSG is reportedly worth €25 million a year, as well as a similar signing on fee.
What has been the reaction of Barcelona fans?
'Devastated' would seem to sum up the mood pretty well at Camp Nou.
Barcelona supporters gathered outside Camp Nou after hearing their hero would no longer continue at the club and several kept a vigil outside the superstar's house on Monday hoping for a last-minute twist to the saga.
Alas, it was not meant to be. Our European football correspondent Andy Mitten spoke to season ticket holders whose ire was directed at both club and player.
"The loyalty to the club towards its players and not being ruthless put Barca in this position," said one. "He felt he deserved to be paid a lot and he did lift up Barcelona, his statistics were unbelievable. But maybe he’s been greedy too," said another.