Chelsea have signed Spain World Cup striker Diego Costa from Atletico Madrid, the Stamford Bridge club said
The transfer fee was not disclosed but the 25-year-old Brazilian-born player's buyout clause at Atletico was about 40 million euros ($54.56 million).
Costa becomes Chelsea manager Jose Mourinho's second major capture of the close season following the signing of his World Cup team mate Cesc Fabregas from Barcelona last month.
Earlier in the day the club announced that Cameroon striker Samuel Eto'o had left the 2012 European champions after spending one season in London.
Costa joins another World Cup team mate, Fernando Torres, and Senegalese international Demba Ba as Mourinho's forward options next season.
Unspectacular early career
It took Costa a while to realise his potential, in part because of injury, and he had unspectacular loan spells at a number of top-flight Spanish clubs including Celta Vigo and Rayo Vallecano.
Atletico won La Liga and reached the Champions League final largely due to Costa's goals as he filled the void left by the departure of Colombia striker Radamel Falcao for Monaco.
Costa raised hackles among his compatriots when he accepted an invitation late last year to play for world and European champions Spain.
However, he was a disappointment at the World Cup in Brazil last month, failing to score against Netherlands and Chile and being left out of the meaningless Australia game as the holders crashed out in the first round.
Chelsea, who finished third in the Premier League last season, start the new campaign with a trip to promoted Burnley next month.