The 17-year-old has made a big mark in the Red Devils' youth team since arriving on scholarship terms from Charlton Athletic last year.
Ramazani, who was born in Burundi but represents Belgium at age-grade level, has now committed his foreseeable future to United.
Posting on his personal Instagram page, the former Charlton winger said: "Happy to sign my first professional contract with @manchesterunited hopefully many more to come!"
A post shared by Largie Ramazani (@lramazani.88) on
Ramazani is now expected to challenge for a spot in United's development squad over the next 12 months.