Tiemoue Bakayoko joins Chelsea from Monaco on a five-year deal
Chelsea have announced the signing of midfielder Tiemoue Bakayoko from Monaco.
The 22-year-old, who played a leading role in Monaco's run to the Champions League semi-finals last season has signed a five-year contract at Stamford Bridge.
The France international has reportedly cost the Blues around £40million.
He told the club website: "I am very happy to be here and to join this great team. I have grown up watching Chelsea. Signing was the natural thing for me because it is a club I loved very much in my childhood."
Bakayoko, who also helped Monaco win the Ligue 1 title last term, added: "I am now looking forward to evolving under this fantastic coach and alongside so many great team-mates."
Chelsea technical director Michael Emenalo said: "Tiemoue was outstanding as Monaco emerged as one of Europe's best sides last season and we are delighted to welcome him to Chelsea.
"Despite his young age he already has plenty of experience as a French title winner and having competed in the latter stages of the Champions League, we believe he will add considerable quality to our squad."
The imposing defensive midfielder will add considerable power and energy to Antonio Conte's side, but his signing raises further doubts about the future of Nemanja Matic.
Matic, Press Association Sport understands, is set, along with striker Diego Costa, to miss the champions' pre-season tour to Asia, which begins next week.
He has been strongly linked with a move to Manchester United and Juventus. Bakayoko would be a like-for-like replacement.
Bakayoko, who joined Monaco from Rennes in 2014 and made his senior France debut in a friendly loss to Spain earlier this year, is Chelsea's third summer signing.
Centre-back Antonio Rudiger arrived from Roma for a reported £29million while veteran former Manchester City goalkeeper Willy Caballero joined on a free transfer.