Nemanja Matic has completed his move from Chelsea to Manchester United, where he will join up with Jose Mourinho for a second time.
The Serbia international has signed a three-year deal with an option for a further 12 months at Old Trafford and follows in the footsteps of the likes of Mark Hughes, Juan Sebastian Veron and Juan Mata in signing for both clubs, after a reported fee of £40million was agreed.
It is the second time Mourinho has brought in the midfielder, having signed him from Benfica in January 2014.
Matic's switch comes after Chelsea completed a deal to bring Tiemoue Bakayoko to Stamford Bridge from Ligue 1 champions Monaco.
Under Mourinho, Matic, 29 on Tuesday, won the double of Premier League and League Cup in 2014-15, before regaining the league crown with Antonio Conte at the helm last season.
Mourinho said: "Nemanja is a Manchester United player and a Jose Mourinho player. He represents everything we want in a footballer; loyalty, consistency, ambition, team player.
"I would like to thank him for his desire to join us because without that, it would be impossible to have him here. I am sure our players and supporters will love him. A big welcome to our new number 31."
Matic added: "I am delighted to have joined Manchester United. To work with Jose Mourinho once again was an opportunity I couldn't turn down.
"I have enjoyed my time at Chelsea and would like to thank the club and the fans for their support. I cannot wait to meet my new team-mates and to start training with them.
"This is a very exciting time for the club and I am looking forward to playing my part in creating more history for this great club."