Greenwood is a product of the club’s famed Academy and has been at Manchester United since the age of seven.
The 19-year-old, who is United’s youngest-ever goalscorer in European competition, has already made 82 appearances for the club. Greenwood is one of nine Academy graduates who have featured in a first-team matchday squad this season.
Mason Greenwood said: “When you join the club at seven years old, you just dream of playing for the first-team one day. I’ve worked so hard to reach this level and the last two years have been amazing.