Chelsea signed David Luiz from Benfica for a reported €25 million ($34 million) on Monday, the Brazil defender joining on a 5 1/2-year contract shortly after Spain striker Fernando Torres had also moved to the English club.
Luiz's transfer means reserve Chelsea midfielder Nemanja Matic will move to Benfica in the offseason. The Serb will remain on loan at Dutch club Vitesse Arnhem until the end of the season.
Luiz had made 82 league appearances since signing for Benfica in 2007, helping the club win last year's Portuguese league title.
"It is a major challenge for me but I am determined and confident in my ability to adapt to this excellent league," the 23-year-old Luiz said in a statement on Chelsea's website.
The Sao Paulo native is ineligible to play in the Champions League for Chelsea this season as he has already appeared in the tournament for Benfica.
Luiz, who was also reportedly a target of Real Madrid this season, initially began his career at Vitoria before moving on loan to Benfica. That transfer was made then made permanent.
Luiz becomes Chelsea's third current Brazilian player, after midfielder Ramires and center back Alex.
Torres' transfer to Chelsea from Liverpool on the final day of the January transfer window was worth a reported 50 million pounds, a British transfer record.