Formerly on the books of Manchester City, the attacker moved out to Germany for regular first-team football as he saw no pathway to the senior side at the Etihad three years ago.
That means he is yet to play in the Premier League and the Watford-born player, who can also play as a No 10 or as a left-sided winger, is keen to conquer his homeland.
He will join up with a rejuvenated United team that includes a number of his England team-mates in Marcus Rashford, Harry Maguire and Jesse Lingard.
And Sancho will help make up one of Europe’s fiercest attacks alongside the likes of Rashford, Anthony Martial and Mason Greenwood, supported by midfielders Paul Pogba and Bruno Fernandes.
Having secured Champions League football for next term, United will hope to both be a real threat on the continent as well as domestically, as they seek to catch up to Liverpool and Manchester City in the English top-flight.