At the age of just 18, Yoro has already played 60 first-team games for Lille OSC. Last season, he was named in the Ligue 1 team of the season having helped his club finish fourth in the league.
Leny Yoro said: “Signing for a club with the stature and ambition of Manchester United so early in my career is an incredible honour.
“Since my first conversations with the club, they set out a clear plan for how I can develop in Manchester as part of this exciting project, and showed a lot of care for me and my family.