Ferguson has had a career the likes of which will never be seen again and he won his 49th trophy this season with United's 20th Barclays Premier League title.
He said: "Sir Alex Ferguson's achievements are truly remarkable - he is genuinely one of the greatest managers of all time and certainly of the modern era. His contribution to English football has been outstanding in every regard and, in the FA's 150th year, it is something that should be celebrated. On behalf of the FA I'd like to wish him a happy and healthy retirement."
First-team coach Rene Meulensteen was told of Ferguson's plans on Wednesday morning and felt the news was not entirely unexpected.
"(I found out) this morning when I came to the club," he said on Sky Sports News. "He called us into his office and he said what decision he took. It's always been on the cards - there's speculation every season. I think the manager kept his cards close to his chest. I think he felt the time was right now and he made a decision.
"He's obviously a man who thinks very, very well so I'm sure he's taken a lot of thought into making this decision. I wish him well. He's been fantastic for this club and I hope all the fans give whoever's going to come in the same support that he gets."
Meanwhile, former United defender Steve Bruce believes any successor to Ferguson will struggle to get close to emulating his record. Hull manager Bruce said Everton boss David Moyes, the early favourite to replace Ferguson, had done well enough at Goodison Park to be able to take on the United job.
"He's cut out of the same cloth (as Ferguson) so it wouldn't surprise me," Bruce told Sky Sports News.
Former Chelsea boss Jose Mourinho has also been linked with moving to Old Trafford when he leaves Real Madrid in the summer.
Bruce said: "Whoever takes over to replace him, whether it's Jose or David Moyes or whoever it is, it's going to be some act to follow. It's impossible to copy somebody like him. He will treat the groundsman just as well as he will treat his star centre-forward. He's got a fantastic humility about him, for all that he's achieved."
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- Sir Alex Ferguson
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