Ferdinand, 35, signed a one-year extension last year after an excellent 2012-13 campaign, however, like the majority of United's players under David Moyes, he has experienced a wretched season and made a relatively low 23 appearances.
"I have thought long and hard over the last few months about my future, and after 12 fantastic years playing, for what I regard, as the best club in the world, I have decided the time is right for me to move on.
"I joined Manchester United in the hope of winning trophies, and never in my wildest dreams could I have imagined how successful we would be during my time here. There have been so many highlights, playing alongside some great players who have become good friends, winning my first Premier League title and also that fantastic night in Moscow are memories that I will cherish forever.
"Circumstances didn't allow for me to say goodbye the way I would have liked but I'd like to take this opportunity to thank my teammates, staff, the club & the fans for an unbelievable 12 yrs that I'll never forget. Winning trophies I dreamed about as a kid came true at this great club.
"I am feeling fit and healthy, ready for a new challenge and looking forward to whatever the future holds for me."
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Ferdinand scored the winner in Sir Alex Ferguson's last career victory against Swansea
Interim manager Ryan Giggs said after United's final home game against Hull last week he had arranged for Ferdinand's last match at Old Trafford to be against Sunderland, when his children were mascots, three days earlier.
Yet following the tawdry manner of Moyes' dismissal last month, Ferdinand was apparently told he was being released by executive vice-chairman Ed Woodward in the away dressing room after United's final game of the season at Southampton on Sunday.
Others were, allegedly, "present at the time" and "expressed surprise" at Woodward's timing, according to the Mail.
Rio Ferdinand's United career
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The John Travolta revival went down surprisingly well with Sir Alex Ferguson
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Debut, vs Zalagerszeg in August 2002
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Title no.1 in 2003
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A regretful Ferdinand looks on after the FA announced he would be banned eight months for missing a drugs test
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Limping out for 2/3 of the year at Wolves in January 2004
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Coming back against Liverpool in September 2005 (credit:Getty Images)
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Ferdinand was named man of the match after a terrific display (credit:Getty Images)
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Goal no.1 vs Wigan
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Goal no.2 vs West Brom
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Liverpool, a team Ferdinand scored against with Leeds, are on the receiving end of a 90th-minute winner in January 2006
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With Nemanja Vidić, Ferdinand has forged one of United's greatest defensive partnerships
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Liverpool get 'merk'd' again in October 2006
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Title no.2, 2007
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A first - and only - Champions League goal for United in Kiev, October 2007
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Enjoying a fortuitous goal at Villa Park later that month
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Ferdinand savours his volley against Newcastle in January 2008
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Title no.3, 2008
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European champion
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World champion (credit:Getty Images)
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League Cup winner for a second time in 2009
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Title no.4
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Title no.5, 2011
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Still going strong
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Manchester United's English defender Rio Ferdinand (R) celebrates scoring his team's second and winning goal during the English Premier League football match between Manchester United and Swansea City at Old Trafford in Manchester, northwest England, on May 12, 2013. AFP PHOTO / ANDREW YATES RESTRICTED TO EDITORIAL USE. No use with unauthorized audio, video, data, fixture lists, club/league logos or “live” services. Online in-match use limited to 45 images, no video emulation. No use in betting, games or single club/league/player publications (Photo credit should read ANDREW YATES/AFP/Getty Images) (credit:Getty Images)
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Manchester United's English defender Rio Ferdinand lifts the Premier League trophy after the English Premier League football match between Manchester United and Swansea City at Old Trafford in Manchester, northwest England, on May 12, 2013. AFP PHOTO / ANDREW YATES RESTRICTED TO EDITORIAL USE. No use with unauthorized audio, video, data, fixture lists, club/league logos or “live” services. Online in-match use limited to 45 images, no video emulation. No use in betting, games or single club/league/player publications (Photo credit should read ANDREW YATES/AFP/Getty Images) (credit:Getty Images)
Manchester United Premier League Winners Parade(26 of26)
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MANCHESTER, ENGLAND - MAY 13: Rio Ferdinand of Manchester United uses the microphone to get the crowd singing at the start of the Premier League trophy winners parade on May 13, 2013 in Manchester, England. (Photo by Christopher Furlong/Getty Images) (credit:Getty Images)
A £29.1 million signing from Leeds United in 2002, Ferdinand won six Premier League titles, two League Cups, the Champions League and the Club World Cup at Old Trafford.
That glittering haul did not help his relationship with Moyes, who showed the former England captain footage of Everton centre-back Phil Jagielka, suggesting Ferdinand model his game on a player who has won nothing.