Michael Essien has completed his move to AC Milan after spending eight-and-a-half years at Chelsea, according to the English Premier League club.
We would have been happy had he stayed because he is a fantastic player for the team but he's given everything for the club and a great chance arrived for his future
The Ghana midfielder joined the Londoners in 2005 during which time they won the Champions League, the Premier League twice and the FA Cup four times.
Essien spent last season on loan at Real Madrid and made 256 appearances for Chelsea, scoring 25 goals.
"To show Michael respect is to not stop him going," manager Jose Mourinho told the club's website.
"We would have been happy had he stayed because he is a fantastic player for the team but he's given everything for the club and a great chance arrived for his future.
"I know he can continue to play at a high level and I wish him success and happiness in Italy and at the World Cup in Brazil," said Mourinho.
The midfielder held talks with new Rossoneri manager Clarence Seedorf last week.
There had been reports in the Italian media, which Essien later quashed on Twitter,suggesting he had failed a medical.
Essien helped Chelsea to win the Champions League - although he was an unused substitute in their 2012 final triumph over Bayern Munich - as well as two Premier League titles and four FA Cups.