Chelsea have completed the signing of Anzhi Makhachkala midfielder Willian on a five-year contract.
The 25-year-old had been linked with a move to Premier League rivals Liverpool and Tottenham during the transfer window, but the Stamford Bridge outfit have now won the race for his signature.
The Brazil international was officially presented by the club on Wednesday, after he was granted a work permit to play in England.
Willian told the club's official website: "I'm very happy to be here, it's been a dream of mine to come and play here.
"Chelsea are one of the best clubs in the world, and now I'm going to play for one of the best managers in the world (Jose Mourinho), so I'm very happy and looking forward to it."
Willian started his career at Corinthians before moving to Ukrainian champions Shakhtar Donetsk in August 2007.
He scored twice when Chelsea met Shakhtar in last season's UEFA Champions League group stages in November, a game the London side won 3-2.
He only joined Russian outfit Anzhi in January, but the club have since looked to trim their wage bill.
Chelsea have been busy in the transfer window, as Mourinho looks to build a side capable of challenging for the Premier League title.
Willian joins goalkeeper Mark Schwarzer, midfielder Marco van Ginkel and forward Andre Schurrle in making the switch to Stamford Bridge.
Chelsea sit top of the league after taking seven points from their opening three games, including a 0-0 draw away to Manchester United at Old Trafford on Monday.