FINALLY - Paul Pogba signs to Manchester United for a record amount of money
The five-year deal marks the second time United has welcomed Pogba - he played for them under Alex Ferguson in 2011, but the club sold him to Juventus a year later for £1.5 million.
That means United has paid almost 60 times more for Pogba than they sold him for just four years ago.
The £89 million figure is more than the previous £85 million record Real Madrid paid for Gareth Bale in 2013.
Commenting on his return, Pogba said:
"I think it's destiny, I would say it's destiny. First my mum told me I would come back here and I told her, 'You never know, you'll see.' For myself as well it's a big challenge too, just to come back to where I came from, where I grew up, where I started. I didn't finish what I started here so I think I came here to finish it."
He added that he would be much better for United since the last time he was at the club:
"I'm more experienced, I've won titles at Juventus. I've been playing with big players like when I started at Man United, of course. I came back. I've not come back from the Academy now; I went to play somewhere else and I came back, I would say, as a person, as an adult. I would say with experience, with more games, so I think that's the difference."
Pogba had a summer vacation in the United States as rumours over his record-breaking transfer to United reached fever-pitch.
Although Mourinho said over the weekend that he was "proud" that United still had the capacity to attract player of Pogba's capacity, some have wondered if he is really worth the money, with ex-player Paul Scholes suggesting Pogba's scoring rate simply isn't high enough.
Premier League fans will not have a long wait to find out if Pogba is a good investment - United's first game is at Bournemouth on August 14.