Ukraine international Andrii Shevchenko has completed his move to Milan from Chelsea after passing a medical.
The 31-year-old spent two seasons at Stamford Bridge after signing from Milan for about £30m in 2006, but has failed to make an impact in England.
“I’m so very happy to be here,” he told the Italian club’s official website.
“At this special moment, I want to send a message to the Chelsea fans who have always made me feel their support. A heartfelt thank you for that.”
Shevchenko, Milan’s second-most prolific goalscorer of all-time, with 127 goals from 208 games, scored only nine goals in 47 appearances.
“It was unfortunate I suffered a number of injuries during my time here but I always gave my all, whatever the circumstances”, he said.
“I really have enjoyed playing in England and have made many friendships that will stay with me forever.
“I will always look back with fond memories of my time at this really great club, and I would also like to express my gratitude to Roman Abramovich for all his help and encouragement.”
Milan vice-president Adriano Galliani said that the striker’s return to the San Siro was not solely down to the club’s owner Silvio Berlusconi.
“This is a family and we’re all happy,” he said.
“It’s not true that only Silvio Berlusconi insisted that Andriy return. I’ve put my weight behind the cause too and I’m happy that in the end we’ve succeeded in bringing him home.”
He added: “After a series of frenetic phone calls during the whole day, we reached an agreement with Chelsea.
“We have managed to bring home a player who has scored the most goals in our shirt in the last 50 years.”