He has overseen countless players coming and going, worked with some of the best and has created an almost seamless series of squads capable of dominating the Premiership.
Behind each of these squads lurk pivotal decisions that have inspired them to achieve so much.
Here are his 10 best decisions, to date.
A former Manchester United player and goal scorer in the side's 1968 European Cup final victory, Brian Kidd was brought back to Old Trafford in 1984 to serve as a youth team coach, only four years after retiring as a player.
When Sir Alex Ferguson's then-assistant Archie Knox left the club in 1991, the Scotsman promoted Kidd to the no. 2 role, a position he held for the next seven years.
While playing a key role in the development of the likes of Ryan Giggs, Paul Scholes and David Beckham, Kidd was on hand to oversee a golden period for the club in the mid-90's.
A man born to be an excellent wingman, Kidd now serves as Roberto Mancini's assistant at defending Premier League champions Manchester City.
Arguably the greatest goalkeeper to ever line up between the sticks for Manchester United, Peter Schmeichel is a true Old Trafford legend, having been a vital member of the squad during the '90's.
His signing in 1991 for only £505,000 may have been considered a steep sum then, but Sir Alex has since described it as the "bargain of the century" (via BBC).
The towering Dane was a domineering presence in the United box during games and always deserved his fair share of credit for keeping the back four in check.
In his final season with United, he helped to clinch the treble, leaving the club on a real high.
Sir Alex has made quite a few game-changing substitutions while at United, but the most significant have to be the introduction of Ole Gunnar Solskjaer and Teddy Sheringham to the 1999 Champions League final clash with Bayern.
With the side down 1-0 and labouring without key players Roy Keane and Paul Scholes on the pitch, the impact of Fergie's subs effectively won the Red Devils the game.
First, Sheringham neatly turned in a miscued Ryan Giggs shot to level things in stoppage time. Moments later Solskjaer popped up to slam a perfect volley into the roof of the net to leave their German opponents stunned.
Football, eh? Bloody hell.
Forgetting the fact that the 2003 signing of Cristiano Ronaldo eventually made the club close to £70 million when he was sold on to Real Madrid in 2009, the Portuguese superstar's impact at the club was immeasurable.
One of the biggest X-factors ever to have played in the Premier League, Ronaldo scored well over 100 goals during his time at Old Trafford.
He helped the club win three consecutive league titles, as well as a precious Champions League trophy in 2008.
Though he is now battling Lionel Messi to be considered the world's greatest player in Spain, make no mistake: His most significant development as a player came under Ferguson in Britain.
Sir Alex faced a barrage of criticism for his decision to sell United stalwarts Paul Ince, Mark Hughes and Andrei Kanchelskis in the summer of 1995.
Fans protested the sale of three players they considered key to United, while pundits doubted the side's ability to replicate their success with youngsters promoted from the club's youth teams.
But the 1995-96 season proved to be one of the most successful in Old Trafford history as Fergie led the new team to Premier League and FA Cup success.
It must be a nice feeling to be proven right.
Though it may be cheating to include a tactic Sir Alex Ferguson has employed many times as a single decision, it is certainly one that has helped define his reputation and success.
The "mind games" the wily Scot has exerted on opposing managers has helped contribute to many a late-season surge.
In 1996, it was Newcastle United's Kevin Keegan cracking. In 2007, it was Arsenal's Arsene Wenger buckling under pressure. While in 2009, it was Liverpool's Rafa Benitez getting riled up by Fergie's very deliberate public comments.
Britain's top managers will no doubt breathe a huge sigh of relief when Sir Alex eventually decides to retire.
Roy Keane will go down as one of Sir Alex's greatest buys—the tough Irishman won seven Premier League titles and four FA Cups at United.
As captain of the club for a considerable spell, the uncompromising box-to-box midfielder led his team by example with an unquestioned work ethic and unparalleled will to win.
Signed for £3.75 million in 1993, Keane more than justified his price tag over the course of his 12-year stint at Old Trafford.
His legacy as a supreme motivator of men and as an inspirational leader has lived on since his departure in 2005.
Sir Alex Ferguson has long been a manager renowned for his faith in the abilities of youngsters at Old Trafford.
No example typifies this better than his accelerated promotion of the likes of Paul Scholes, Nicky Butt and the Neville brothers to the first team in the 1995-96 season.
Over the course of his tenure, Fergie has never been afraid to throw an inexperienced player in at the deep end, and he is usually proven justified by their performance.
Sorry, Alan Hansen, turns out you can win with kids.
The 2001-02 season was supposed to have been Sir Alex's last at Old Trafford.
But the thought of a life without football clearly didn't appeal to the Scot, who promptly canned his retirement plans in early 2002, much to the relief of United fans.
The decision was an excellent one. In the ten years since, he has won a further five Premier League titles and doubled his Champions League success.
The thought of him leaving the game for good seems unfathomable at present, even though we all know the day will soon come.
As the man whose signing helped turn the club from contenders to champions, it should come as little surprise to see Eric Cantona topping a Manchester United-related list.
Bought for a paltry £1.2 million halfway through the 1992-93 season, the enigmatic, charismatic Frenchman inspired his teammates to greater heights with his effervescent style of football.
The Red Devils won the inaugural Premier League that term and haven't looked back since.
His transfer can be pointed to as being the true catalyst for the club's momentous rise to the summit of world football.
What other Sir Alex decisions are worthy of a mention? Who else would you consider his greatest signings?