Manchester United have announced the signing of Nemanja Matic from Chelsea on a three-year deal.
The 28-year-old defensive midfielder joins for a fee believed to be £40m and re-joins manager Jose Mourinho, who brought him back to Chelsea in January 2014.
Matic becomes the Portuguese's third signing of the summer after Romelu Lukaku (£90m) and Victor Lindelof (£39.5m) and takes United's summer spending to over £150m.
The Serb said: "To work with Jose Mourinho once again was an opportunity I couldn't turn down. 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.. I have enjoyed my time at Chelsea and would like to thank the club and the fans for their support."
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."
Mourinho was keen to add a defensive midfielder to his squad this summer and wanted to sign Eric Dier, but Tottenham insisted the England international was not for sale.
Matic was his second target and, despite Chelsea being understood to prefer to sell him abroad and interest from Juventus, the former Benfica man was keen to make the move to Old Trafford.
He was left out of Chelsea's pre-season tour to Asia and the Blues have also signed Tiemoue Bakayoko from Monaco in his position to compete with N'Golo Kante.
Matic will now prepare for Manchester United's next pre-season friendly against Sampdoria on August 2 and then Real Madrid in the European Super Cup three days later.
Mourinho said last month that he wanted at least a fourth signing if possible, and the club now have a month left of the window to land their top target; Inter Milan's Ivan Perisic.