Lille defender Leny Yoro has completed his move to Manchester United in a deal worth up to £58.9m.
It was thought Real Madrid were the Frenchman's preference, but United worked hard to convince the 18-year-old to join after agreeing a deal worth an initial £52.2m, with potential add-ons worth almost £7m.
Yoro has signed a five-year contract at Old Trafford with the option of a further 12 months.
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.
"I know about the history of young players at Manchester United and feel it can be the perfect place to reach my potential and achieve my ambitions, together with my new team-mates. I cannot wait to get started."
'One of the most exciting young defenders in world'
Manchester United sporting director Dan Ashworth said: "Leny is one of the most exciting young defenders in world football; he possesses every attribute needed to develop into a top-class centre-back.
"Having had such an excellent start to his career, we are excited to support him in reaching his immense potential here at Manchester United.
"This club has a fantastic record of developing young players, whether homegrown or brought in from elsewhere, and giving them the required guidance, time and patience to grow and flourish.
"Under Erik ten Hag and our excellent staff we will ensure that Leny has the perfect platform to achieve the success that everyone across the club is aiming for."
Everton defender Jarrad Branthwaite and Bayern Munich's Matthijs de Ligt are players the club still admire - and remain options, subject to having budget and squad space available as the window evolves.
Signing two central defenders this summer is possible for Man Utd boss Erik ten Hag following the exits of Raphael Varane and Willy Kambwala, and further departures would increase that likelihood.
The signature of Yoro comes with Lille finding themselves in a difficult situation because he had one year left on his deal and can speak to clubs outside of France from January.
Yoro made 41 appearances in all competitions for the Ligue 1 side last season and scored three goals.