Chelsea have completed the signing of striker Andriy Shevchenko from AC Milan for a fee of about £30m.
The 29-year-old signed a four-year contract on Wednesday after agreeing personal terms and passing a medical.
"I am here for the challenge and the excitement of the Premier League," said the Ukraine captain.
The exact fee has not been disclosed, but it is believed it beats the £30m Manchester United gave Leeds in 2002 for England defender Rio Ferdinand.
It is certainly a club record fee for Chelsea, eclipsing the £24.5m they paid for Lyon's Michael Essien in 2005.
"For him to leave Milan for Chelsea is a big statement about where Chelsea is"
Shevchenko, former European Footballer of the Year, added: "I am going from one big club to another and joining a team of champions.
"There is a right moment to join a football club and I think I have arrived here at the perfect time.
"The Champions League has to be a realistic target for next season but it is not just about the Champions League. Chelsea is going for their third Premiership as well and I like the club's mentality of wanting to win every game they play.
"I have followed Mr (Jose) Mourinho's career carefully for the last few years and have been hugely impressed with the way he manages.
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"He puts team ethic before individual expression which is the way I believe great teams are created.
"Had money been my motivation for coming, I would probably have stayed in Milan.
"I am pleased that Chelsea managed to conclude everything before the World Cup - I can go to Germany with a clear mind and proud to be a Chelsea player."
Chelsea manager Mourinho said: "Today is a day when the dream became reality. Andriy has always been my first choice for Chelsea since I arrived.
"Before it was not possible, now it is for real. He has great qualities, ambition, discipline, tactical awareness and of course he is a great goalscorer.
"I did not need to meet with him to convince him about Chelsea, in the same way we did not need to talk a lot about why I wanted him. Everybody knows him as a player, tactically he can play in the Chelsea system no doubt.
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"Milan is a big club, a great club, but for him to leave Milan for Chelsea is a big statement about where Chelsea is.
"He is a champion and he is joining a team of champions. I have already spoken to some of our players and they are looking forward to playing with him. Great players want to play with other great players."
Chief Executive Peter Kenyon added: "The deal is a new club transfer record and is a straight cash deal. We are delighted to have signed one of Europe's greatest goalscorers."
The news that Shevchenko had finalised his switch was first broken by AC Milan's website, which said in a statement: "AC Milan communicates it has ceded definitely the sporting rights of Andriy Shevchenko to Chelsea."
The club swiftly released another statement saying: "Milan thank Shevchenko, an extraordinary man and striker, for the great amount of excitement he provided in the seven seasons in which he wore the red and black shirt.
"His 173 goals, making him the second top scorer in the club's history, have contributed in a vital manner to the winning of an Italian league title, an Italian Cup, Super Cup, a Champions League and a European Supercup."
Shevchenko, born in Dvirkivshchyna, Ukraine, on 29 September 1976, began his career with Dynamo Kiev, making his debut as a teenager in 1994.
In 1997-98, when already a Ukraine international, he sprung to the attention of the European game when he scored a hat-trick in a 4-0 win over Barcelona at the Nou Camp.
In 1999 he joined AC Milan and was an instant success - going on to win the European Footballer of the Year prize in 2004.
He has also led his country to their first World Cup finals.
Shevchenko becomes Chelsea's third signing of the summer after midfielder Michael Ballack from Bayern Munich and Feyenoord striker Salomon Kalou.
Mourinho is also reported to be interested in signing Real Madrid and Brazil defender Roberto Carlos and goalkeeper Hilario from Portuguese club Nacional de Madeira.