The young shot-stopper had been at Fleetwood&aposs academy since the age of eight, moving into his role between the posts halfway through a four-year spell after showing quality in that area of the pitch.
The League One club have confirmed that they will receive a &apossignificant training compensation fee&apos from United for Hartley, who will join up with the academy set-up.
Hartley becomes the fourth goalkeeper to join United over the last few months and is by far the youngest. The club have overseen a major overhaul in that area of the pitch, following the departure of four shot-stoppers.
David de Gea was released upon the expiration of his contract at the start of summer, calling time on a 12-year spell at the club, while Dean Henderson joined Crystal Palace in a deal worth 20million plus add-ons. Young goalkeepers Nathan Bishop and Matej Kovar also left.
To fill the gaps, United spent 47.2million on Andre Onana, bringing in the former Inter Milan man as Ten Hag&aposs first-choice option. They also signed Altay Bayindir from Fenerbahce for 4.3m, with the Turkish international coming in as back-up.
United also signed free agent Kie Plumley last week, following his release from Oxford United. The 20-year-old has joined up with the club&aposs youth sides and is expected to offer a back-up option across the age groups.
Manchester United are back in the Champions League after an impressive first season in charge for Erik ten Hag.
Having won the famous trophy three times, the Reds have a wonderful history in the European Cup. Now the Dutchman has to live up to that legacy.
Our special preview of Uniteds 2023/24 Champions League campaign provides the ultimate guide to the tournament.