Chelsea have signed Monaco striker Radamel Falcao on a season-long loan deal, with the option to make the deal permanent.
The 29-year-old Colombia international spent last season on loan at Manchester United, scoring four goals in 29 games.
He links up with former Atletico Madrid team-mates Thibaut Courtois, Filipe Luis and Diego Costa.
Croatian midfielder Mario Pasalic, 20, goes the other way on loan for the season.
Falcao said: "I am very happy to be joining Chelsea.
"I can't wait to start training, to help with our aim of retaining the league title and being successful in Europe."
The striker scored 72 goals in two seasons for FC Porto between 2009 and 2011, before joining Atletico Madrid.
After 70 goals in two prolific seasons with the Spanish side, Monaco signed him for £50m in 2013.
He suffered anterior cruciate ligament damage in January 2014 and joined United on loan that summer.
Falcao and Costa have previously played up front together for Atletico and won the 2013 Copa del Rey final against Real Madrid.
Pasalic, who signed for Chelsea from Hajduk Split 12 months ago, spent last season on loan with Elche in La Liga.