The 21-year-old star is now the second-most expensive English player in history, behind only his new club colleague Harry Maguire.
United coughed up around £76.50 million to bring Sancho to Old Trafford, which is a serious amount of money.
However, it's quite likely that the sizeable investment will prove to be worth every single penny.
Despite his young age, Sancho is already one of the best attack-minded players in the world today and he will only get better in the coming years.
At Dortmund, the former Manchester City starlet scored 50 goals and contributed 64 assists in his 137 appearances across all competitions.
That is world-class output and it's numbers like the ones above which have resulted in ex-Liverpool midfielder Didi Hamann boldly labelling Sancho as "the best winger in the world".
Speaking exclusively to Racing Post, the German said: “It's a big season for Ole Gunnar Solskjaer and Manchester United too and I expect Jadon Sancho to be a star at Old Trafford.”
“I've rarely seen a winger who can beat his man so easily, he drops the shoulder and just walks past defenders.”
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“Sancho could galvanise the likes of Marcus Rashford and Paul Pogba at United too. Having watched him in the Bundesliga, he makes other players better, creating chances and pulling defenders out of position, and we saw glimpses of that in England's quarter-final win against Ukraine at Euro 2020.”
“I was surprised that he was on the periphery of that tournament, he would be my first choice as a manager.”
“In my view, not only is Sancho England's best winger, he’s the best winger in world football and United fans should be very excited about his return to Manchester.”
That's a huge claim from Hamann, although Sancho's goal and assist records at Dortmund do speak for themselves.
That being said, can a player that struggled for game time at a major international tournament really be the best in the world? In our opinion, no.
Sancho is already world-class, that we don't doubt, but he has a long way to go before he can be recognised as the world number one in his position.