The winger still has to complete his contract and undergo medical tests with United after he finishes with England at the European Championship.
The 21-year-old Sancho is yet to start for England at the tournament heading into the quarterfinals, despite his growing stature.
Sancho started his career at Manchester City’s academy but rejected a deal to stay and joined Dortmund in 2017. He has scored 50 times in his 137 appearances since moving to Germany.
Now he is set for City’s fierce local rival to help United’s bid to dethrone its neighbor as Premier League champion. The new season starts for United on Aug. 14 against Leeds.
Sancho become the second most expensive English player behind Harry Maguire, who United signed two years ago from Leicester for 80 million pounds ($97 million).