Chelsea have signed Fiorentina winger Juan Cuadrado for an initial fee of £23.3m, with Mohamed Salah going the other way on loan.
Cuadrado has signed a four-and-a-half-year contract for a fee which could rise to £26.8m.
The 26-year-old, who impressed for Colombia at the World Cup, joined Chelsea after fellow winger Andre Schurrle moved to Wolfsburg for £22m.
Salah, 22, moves to Serie A side Fiorentina until the end of the season.
The Egypt winger has made 19 appearances for Chelsea since joining the club from Basel for a fee in the region of £11m in January 2014. However, he has only started six Premier League games.
New Chelsea signing Cuadrado said: "I am very happy and thankful for this opportunity I've been given. This is a great club and honestly it is like a dream to join the Chelsea family and to know that the manager believes in me. I'm happy."
It is thought Cuadrado, who has scored five goals in 37 international appearances, had a release clause in his contract of £26.8m.
Cuadrado played in Italy for five and a half years, initially joining Udinese from Medellin in his homeland in 2009. After a loan spell at Lecce, he moved to Fiorentina in 2012 and scored 20 goals in 85 Serie A appearances for the Florence side.
Fiorentina coach Vincenzo Montella revealed the deal was imminent on Friday, saying: "It was a sale that had to be done.
"Cuadrado is a player that has always arrived with a smile and given everything to Fiorentina - I'm happy for him because he is going to a big club."
South American football expert Tim Vickery
"James Rodriguez was Colombia's undoubted World Cup star - but Juan Guillermo Cuadrado was not far behind.
"Chelsea's new acquisition solved Colombia's tactical problem. The defensive line had to sit deep to protect veteran centre back Mario Yepes. It was Cuadrado who kept dragging the team forward and opening up the pitch with his sustained pace and effervescent dribbling down the right flank.
"He is at his best as a wide right-midfielder - especially as over the last couple of seasons he has started scoring more goals. But he can also feature as an attacking right-back, or cut in from the other flank.
"Some three years ago a Premier League giant had a look at Cuadrado but concluded that he was too old - a strange decision given that he is still only 26, and should be looking forward to playing his prime years under Jose Mourinho, who will certainly enjoy the pace on the transitions that his new Colombian acquisition will bring to the side."