Benfica have announced they have agreed a deal to sell defender David Luiz to Chelsea.
Reports suggest that an initial £21million deal has been agreed, with Chelsea set to pay £17m of the fee up front.
The Brazilian has penned a five-and-half-year contract at Stamford Bridge and admits he is excited by the challenges posed by life in the Premier League.
He told the Blues' official website: "I am delighted to be joining a big English club, and I know very well the quality that Chelsea has.
"It is a major challenge for me but I am determined and confident in my ability to adapt to this excellent league, and I look forward to meeting my new-team mates."
On the capture of Luiz, Chelsea chief executive Ron Gourlay said: "David Luiz is one of the great defensive prospects in world football, and already a Brazilian international. I am sure he will prove a valuable addition to the Chelsea squad."
Chairman Bruce Buck added: "It is a delight to have completed this transfer for a fantastic young footballer who we have admired for some time. David has played in the Champions League and the squad now has a more experienced look to it that will hopefully serve us well for the rest of this season and going forward."
The deal will take Nemanja Matic in the opposite direction, with the Serbian midfielder set to link up with Benfica over the summer once his loan deal at Vitesse Arnhem comes to an end.