The 16-year-old took to Instagram to announce the move, writing:
"Happy and proud to announce my signature in this great club and big Family which is @manchesterunited. A big thank you to my parents, to Badou my lawyer, my loved ones and the coaches (from Sannois, Amiens and INF) who have made me grow up to this day. This is the beginning of a new and great adventure if God wants it. #MUFC @amiensscfootball."
It was expected that the young winger, who has represented France's under-16s, would join the club in January but it has taken until mid-February for the deal to be wrapped up.