The 71-year old has drawn the curtain on a 26-year career at Old Trafford, paving the way for fellow Scotsman David Moyes to take the reins when he leaves Everton in the summer.
Below are just a few of the many reactions to both announcements starting with some love for Fergie from some of his past pupils.
United great Edwin van der Sar was somewhat surprised at Fergie's decision.
van der Sar's fellow former gloveman Peter Schmeichel was in disbelief.
Let's hope the 'Major announcement' at 2.30 is Ronaldo coming back rather than SAF stepping down. #SAFmustSTAY— Peter Schmeichel (@Pschmeichel1) May 8, 2013
Disappointed, shocked, sad. Didn't think THAT day would be today.— Peter Schmeichel (@Pschmeichel1) May 8, 2013
Andy Cole felt Fergie was the only boss to get the best out of him.
Can't believe the boss has retired, greatman great manager gonna miss him shouting cole. Only manager to have got the best out of me.— Andrew Cole (@vancole9) May 8, 2013
Cole's former strike partner Dwight Yorke added.
Wow.. The news that #SAF has retired has made me very sad. I as a player have been so lucky to have played under such an man. Thank you Alex— Dwight Yorke (@YorkeDwight) May 8, 2013
Mikel Arteta wishes his former Toffees boss Moyes all the best.
All the best to David Moyes.I hope Everton finds the right person to keep moving the club forward!!— Mikel Arteta (@m8arteta) May 9, 2013
Joey Barton had some encouraging words for the Scotsman.
Fergie retires! What an act to follow. All the best to whoever picks up the gauntlet.Looks like Moyes.Big loss for EFC but great opportunity— Joseph Barton (@Joey7Barton) May 8, 2013
Very good appointment by Manchester United. Next years Premier League is going to be the most exciting ever.— michael owen (@themichaelowen) May 9, 2013
Congratulations to David Moyes on his huge appointment and the 6-years contract. A great sign of continuity and long-term strategy! #MUFC— Jürgen Klinsmann (@J_Klinsmann) May 9, 2013
Hope Akpan (@HopeAkpan) May 9, 2013
And Tim Cahill, now with New York Red Bull, also paid tribute to his former manager.
However, Didi Hamann does not believe it is the best time for Moyes to be taking the reins.
Moyes has done great at Everton but United are miles off winning the CL so im not sure whether its a good time to take over— Didi Hamann (@DietmarHamann) May 9, 2013