Manchester United have confirmed the club record £37.1million capture of Juan Mata from Chelsea.
The midfielder was helicoptered into the Aon Training Complex on Saturday morning before completing his medical and agreeing personal terms.
Manager David Moyes has already confirmed Mata will be in his squad for Tuesday's Premier League encounter with Cardiff at Old Trafford.
"I know our fans have admired Juan for some time now - he has always played well against us - and I know they will be delighted to see him in the red of United; starting on Tuesday," said Moyes.
The sum spent on Mata smashes United's previous record outlay - the £30.75million they paid Tottenham for Dimitar Berbatov in 2008.
It underlines the desperation at Old Trafford to prove they are determined to shove United back to the top end of the Premier League after this season's disastrous campaign.
United have slumped to seventh in the table and were eliminated from the Capital One Cup semi-finals by 19th-placed Sunderland on Wednesday.
In addition, they have also been knocked out of the FA Cup, meaning an unlikely Champions League triumph is now their only hope of silverware, in addition to currently being their best route back into the competition next term.
Nevertheless, despite the strife, Mata had no hesitation in jumping at the chance to rebuild his career, which has stalled following Jose Mourinho's arrival at Stamford Bridge, even though he was crowned Chelsea's player of the year in the previous two seasons.
"I am thrilled to be joining United," he said.
"I have enjoyed some very happy years at Chelsea but the time has come for a new challenge.
"United is the perfect place for me and I am excited at the chance I have to be part of the next phase in the club's history.
"Chelsea is a top club and I have many friends there but you cannot turn down the chance to join Manchester United.
"I look forward to helping the manager and the team be successful in the coming years."
Mata is ineligible for the Champions League, meaning his task for the remainder of this season will be to inspire a team whose recent performances have been appalling by their own high standards.
Moyes has clearly noted a lack of invention in his squad, which has only been accentuated by the recent absences of Robin van Persie and Wayne Rooney.
Having been a regular for Spain - one of the major reasons behind Mata's desire to move was to cement a place in his country's World Cup squad next summer - he has the experience and ability to have the kind of instant impact Moyes craves.
"Juan is one of the finest playmakers in the game today and it's a real pleasure to have secured his signature," said Moyes.
"He's been instrumental in Chelsea's recent success, with a notable 28 assists and 32 goals in his last two Premier League seasons.
"I have been impressed with the excitement he has shown to be part of the new Manchester United."
Juan Mata factfile
1988: Born Juan Manuel Mata Garcia on April 28 in the Spanish province of Burgos.
2003: Moves from Real Oviedo's youth ranks to those of Real Madrid.
2006: July 29 - Helps Spain win the European Under-19 Championship, beating Scotland 2-1 in the final.
2007: March - Agrees a move to Valencia effective from the 2007-08 season.
June - Finishes the 2006-07 campaign with 10 goals for Real's B team, Castilla, as they are relegated from the Spanish Segunda Division.
2008: April 16 - Scores in Los Che's 3-1 win over Getafe in the Copa Del Rey final. He had also scored twice in the semi-final win over Barcelona.
2009: March 28 - Makes his senior debut for Spain as a substitute against Turkey.
May - Finishes the 2008-09 season with 11 goals and 13 assists for Valencia.
September 9 - Scores his first goal for Spain in a 3-0 win over Estonia.
2010: June - Makes one appearance in Spain's victorious World Cup campaign, as a substitute against Honduras.
2011: Helps Valencia to a secons successive third-placed finish in La Liga.
June - Named as UEFA's "Golden Player" of the European Under-21 Championship as Spain win the tournament.
August 24 - Signs for Chelsea on a five-year contract. Is given the number 10 shirt after Yossi Benayoun agrees to give it up.
August 27 - Scores on his Chelsea debut as a second-half substitute against Norwich.
September 14 - Does likewise on his Champions League debut for the club, against Bayer Leverkusen.
2012: May 5 - Named man of the match as Chelsea beat Liverpool 2-1 in the FA Cup final. Mata scored four goals and set up another four in the competition.
May 10 - Named Chelsea's fans' player of the season.
May 19 - Sets up Didier Drogba's equaliser as Chelsea win the Champions League final against Bayern Munich, despite Mata's miss in the penalty shoot-out.
July 1 - Scores the final goal as Spain beat Italy 4-0 in the final of Euro 2012.
November 6 - Named Barclays Premier League player of the month for October.
2013: March 3 - Makes his 100th Chelsea appearance in a 1-0 win over West Brom.
April 19 - Nominated for the PFA Player of the Year award, eventually won by Tottenham's Gareth Bale.
May 15 - Helps Chelsea win the Europa League, setting up Branislav Ivanovic's late winner.
May 16 - Named as Chelsea's player of the year for the second successive year, adding the players' player of the year award.
June 15 - Dismisses reports new Chelsea manager Jose Mourinho has told him he is surplus to requirements.
August 29 - Despite rarely selecting him, Mourinho insists Mata has a future at Stamford Bridge.
2014: January 25: Completes £37.1million move to United.