1. Cristiano Ronaldo (£80m) Man Utd-Real Madrid (July 2009)
2. Zlatan Ibrahimovic (£56.5m) Inter Milan-Barcelona (July 2009)
3. Kaka (£56m) AC Milan-Real Madrid (June 2009)
4. Fernando Torres (£50m) Liverpool-Chelsea (Jan 2011)
"I'm so happy and proud to be here," added Torres, who is available to play in the Champions League having only featured in this season's Europa League and could face Liverpool in the league on Sunday.
"It's been two, three, four very hard days for me. I'm really happy - this is a great club. I'm prepared and ready for the challenge.
"I know there are many great players here and I will work hard to win a place in the team.
"I am looking forward very much to helping my new team-mates this season and for many years to come.
"It's my dream to win the Champions League and I'm sure I can, playing for Chelsea."
Blues boss Carlo Ancelotti has selected both Didier Drogba and Nicolas Anelka up front in four of Chelsea's last five league games.
"I am a big fan of all of the Chelsea strikers," said Torres of his competition for a striking berth.
"When I was very young I remember Anelka was playing for Arsenal. Obviously Drogba is the best striker in the world by far.
"It is a big responsibility for me to play alongside them because the level they have is so high."
Torres becomes the fourth most expensive signing in world football behind Cristiano Ronaldo, Zlatan Ibrahimovic and Kaka.
Chelsea chairman Bruce Buck added: "This is a very significant day for Chelsea, capturing one of the best players in the world with his peak years ahead of him.
"We have long admired the talents of a player who is a proven goalscorer in English football and Fernando's arrival is a sign of our continuing high ambitions. I hope every Chelsea fan is as excited as I am with this news."
The Reds rejected a £35m bid from Chelsea after Torres' transfer request was turned down on Friday.
Mark Lawrenson on deadline day activities at Liverpool
But with Torres clearly intent on a move away from Anfield the Reds finally accepted defeat and cashed in on their prize asset.
Manager Kenny Dalglish said earlier on Monday: "Movement is part and parcel of football but the most important people at Liverpool Football Club are the ones who want to be here."
Liverpool had been angered by the timing of Torres' transfer request last week and reportedly believe the London club "tapped up" the player by encouraging him to express a desire to leave.
Torres had a £50m release clause in his contract that entitled him to leave if the Merseysiders, who are seventh in the Premier League, failed to qualify for the Champions League this season.
Torres, who signed a six-year contract when he joined the Reds, had been linked with Chelsea before.
The west Londoners were reported to be interested in luring the Spaniard from Anfield in the summer of 2008 and made a bid in May 2010, but after helping Spain win the World Cup in June, Torres pledged his future to Liverpool.
He said at the time: "My commitment and loyalty to the club and to the fans is the same as it was on my first day when I signed."
Torres notched three hat-tricks in his first season at Liverpool, scoring 33 goals in 46 appearances, and netted the winner as Spain beat Germany 1-0 to win the European Championship in 2008.
Hamstring injuries plagued him during the 2008-09 season but he still managed 17 goals in 38 games, while groin problems and knee surgery disrupted his 2009-10 campaign, although he still managed to find the net 22 times in 32 games.
Torres picked up a World Cup winners' medal with Spain but he failed to score during the finals in South Africa and pulled up with an abductor problem in the final, having come on as an 89th-minute substitute in the 1-0 victory over the Netherlands.
He has endured an indifferent 2010-11 season, scoring only nine goals in 26 games.
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