Chelsea have confirmed Portuguese coach Jose Mourinho as their new manager on a three-year contract.
Mourinho takes over from the sacked Claudio Ranieri at Stamford Bridge after quitting as coach of Porto.
Reports say Chelsea agreed a £1.7m compensation package with Champions League winners Porto.
"Chelsea represent a fantastic challenge for me. It is a great club with a world-class squad of players," the 41-year-old Mourinho said.
And demonstrating the self-confidence that has marked his rise, he said: "We have top players and, sorry if I'm arrogant, but we now have a top manager."
Mourinho added: "The English Premiership is recognised as the best league in the world and I am really excited at the prospect of competing week in, week out at the highest
level in England as well as in Europe.
"I have been asked how I will cope with the pressure, how I will cope with these players, how I will cope with the urgent ambition to win titles.
"You don't have to ask me again because that's what I live for."
And Mourinho, who had also been linked with Liverpool, continued: "English football is a big passion for me. There were some big clubs chasing me very hard.
"This was a fantastic position for me and the people in my boat, and Chelsea was a perfect choice for me.
"I don't want to sound arrogant, but I think I am a special manager because I have won the Champions League."
But he hinted that the vast Chelsea squad will be reduced.
"If all the names I was supposed to be signing arrive, I would have a squad of 50 players.
"I won't work with big squads. I like small squads. I will have 21 outfield players, plus the goalkeepers, because this is the right amount for the specific work we want to do."
Mourinho also confirmed members of the Porto backroom staff will come to join him.
He has long been touted as the successor to Ranieri, who was dismissed after four years in charge despite a contract until 2007.
And Chelsea chief executive Peter Kenyon
was delighted to have got his man.
He said: "The appointment of Jose Mourinho is all about building on the foundations which we have already established at
"He represents the new generation of football coaches and we are convinced he can take us to the next level, both in England in Europe.
"His record of sustained success makes him perfect for what we want to achieve at Chelsea."
Meanwhile, negotiations on Ranieri's pay-off from Chelsea have yet to reach a conclusion.
Kenyon said: "The situation is simple. We will honour Claudio Ranieri's contract in full. We have had discussions over the last 48 hours.
"There is no question we will treat it in any other manner but unfortunately there has been no conclusion."