The Premier League champions confirmed on Wednesday that Ferguson, 71, would step aside at the end of the season.
"The decision to retire is one that I have thought a great deal about and one that I have not taken lightly. It is the right time," Ferguson said on United's website (www.manutd.com).
The Scot took charge in 1986 and his arrival heralded an unprecedented period of success for the club, including 13 English league titles, five FA Cups and four League Cups.
He also steered the club to two Champions League triumphs and FIFA's Club World Cup. DM