The France midfielder flew from Nice into Manchester Airport on Monday before making his way to the club’s training ground.
United will pay the Italian champions 105m euros for Pogba, plus performance-related bonuses and other costs.
The deal for the 23-year-old, who left United for £1.5m in 2012, is due to be completed in midweek.
The Old Trafford club still have to agree personal terms with Pogba, although that is expected to be a formality.
Pogba’s return surpasses Wales forward Gareth Bale’s £85m move to Real Madrid in 2013 as the biggest transfer deal in history.
“Football is crazy and the market has become crazy. What you think this season is crazy, you realize three years later it’s not crazy any more.”What is expensive and not expensive in football? I don’t know any more. I just know he is a big player.”, Jose Mourinho disclosed.
Pogba, who helped France reach the Euro 2016 final, has won the Serie A title in each of his four seasons at Juventus.
He is Mourinho’s fourth signing at United, after Ivory Coast defender Eric Bailly, former Sweden striker Zlatan Ibrahimovic and Armenia forward Henrikh Mkhitaryan.
