The club confirmed on Tuesday morning that Sir Alex Ferguson's successor had "left the club" after less than a season in charge.
Moyes endured a miserable time in charge, with Sunday's 2-0 loss at his former club Everton the latest setback.
It is understood that Moyes was sacked by vice-chairman Ed Woodward during a meeting at the club's Carrington training ground this morning shortly after 8am.
The club had previously backed their manager despite a series of dreadful results, but Sunday's defeat at Goodison Park proved one too many.
With a £150million spending spree planned for the summer the club's owners, the Glazer family, wanted to make sure they had the right man at the helm to bring success back to Old Trafford.
A statement from the club, released at 8:30am, read: "Manchester United has announced that David Moyes has left the club.
"The club would like to place on record its thanks for the hard work, honesty and integrity he brought to the role."
It is understood that long-serving midfielder Ryan Giggs will be announced as interim manager later on Tuesday.
There will be no shortage of takers when it comes to seeking a successor for Moyes, who turns 51 this Friday.
Louis van Gaal is among the front runners. The former Barcelona manager has an impressive CV and will be available this summer when he leaves his post as Holland coach.
Borussia Dortmund coach Jurgen Klopp is among the fans' favourites to take over, but the club are understood to favour other candidates.
Diego Simeone is a highly regarded figure in European football after taking Atletico Madrid to the top of the Spanish league and into the semi-finals of the Champions League.
However, many fans would like to see Giggs take the post on a long-term basis, despite his lack of managerial experience.
Moyes slipped into United's base in Carrington un-noticed on Tuesday morning.
Succeeding Sir Alex Ferguson, who won 13 league titles during his time at the club, was always going to be difficult, but few expected this season to have gone so badly.
The list of unwanted records broken by Moyes is as embarrassing as it is long. United are guaranteed to end the season with their worst points total in Premier League history, they have failed to qualify for the Champions League for the first time in almost two decades while Moyes' home record is the worst of any United boss since 1978 when Dave Sexton was in charge.
The Red Devils are seventh in the Barclays Premier League with four matches to go, with Europa League qualification now also looking unlikely.
Moyes won 27, drew nine and lost 15 of his 51 games in charge.
The Scot was dogged by claims he was not up to the job ever since he took over last July.
Moyes had enjoyed 11 critically-acclaimed years at Everton, leading the club to five top-six finishes. The Toffees qualified for the Champions League for the first time under Moyes' stewardship - although they lost in the qualifying stages of the competition - and he also took the Merseyside club to the FA Cup final in 2009.
But all those achievements were small fry compared to what his predecessor achieved.
The enormity of the task in hand seemed to overwhelm Moyes from day one.
Moyes upset some within the club by bringing in his own coaching staff, while the likes of Rene Meulensteen, Eric Steele, and Mike Phelan departed.
Moyes also botched his first transfer window as United boss. The Scot pursued Barcelona's Cesc Fabregas when the Spaniard had no intention of leaving the SpaniSh giants.
Thiago Alcantara joined Bayern Munich ahead of United, while the club made a real hash of their attempts to sign Marouane Fellaini and Leighton Baines on the cheap.
United's bid of £28million for the pair was branded "derisory and insulting" by Everton.
Baines stayed and United ended up buying Fellaini for £27.5million when they could have bought him for £4million less had they acted quicker.
Moyes rarely looked comfortable in front of the cameras, and for that reason many felt Jose Mourinho, who left Real Madrid to rejoin Chelsea last summer, would have been a better option.
It is understood that no decision has yet been made on the futures of the coaches Moyes brought into United - Steve Round, Phil Neville, Chris Woods and Jimmy Lumsden.
Rumours of player unhappiness with Moyes' tactics training methods persisted throughout his reign, although the Scot always denied there were any problems.
In December, Rio Ferdinand questioned Moyes' policy of naming his starting XI on the day of the game, claiming it turned him into a "madman" wondering whether he was to be selected.
Shortly after United's embarrassing 2-0 defeat at Olympiacos, Robin van Persie complained about his team-mates running into his space on the pitch.
The shock news that Danny Welbeck, an academy graduate born in Manchester, wanted to leave the club, did not go down well with the United hierarchy.
Moyes also oversaw the exit of highly-respected club captain Nemanja Vidic, who will leave for Inter Milan in the summer.
Another senior figure and dressing room stalwart Patrice Evra may follow the Serbian out the door when his contract expires.
Moyes succeeded where Ferguson failed in tying Wayne Rooney down to a long-term contract.
Goalkeeper David de Gea and Adnan Januzaj have also developed well during Moyes' reign, but that cannot be said for the rest of the squad and many supporters became disenchanted with the slow and methodical style of play on show at Old Trafford this year.
David Moyes timeline
1963: Born April 25 in Glasgow.
1980: Signs professional forms with Celtic.
1981: Plays against Juventus in the European Cup and represents Scotland Youth.
1982: Picks up a Scottish Premier League winner's medal.
1983: With chances limited at Parkhead, heads to England and Cambridge United.
1985: Moves to Bristol City.
1987: Signs for Shrewsbury.
1990: Moves back to Scotland with Dunfermline.
1993: After a brief spell at Hamilton, joins Preston in September.
1994: Captains North End in the Division Three play-off final defeat by Wycombe at Wembley.
1995: Preston finish fifth again in the Third Division, but lose to Bury in the semi-finals of the play-offs.
1996: Preston are promoted after winning the Third Division title. Moyes takes an active role in coaching and is eventually appointed assistant to Gary Peters.
1998: January - surprise choice to take over manager's job when Peters switches roles to oversee the Centre of Excellence.
May - Preston finish 15th in Division Two.
1999: North End finish fifth and reach the semi-finals of the Division Two play-offs, where they are beaten by Gillingham.
2000: Preston romp to the Second Division championship, racking up 95 points.
2001: The Lilywhites finish a surprise fourth in Division One. Moyes takes Preston to within 90 minutes of the Premiership, but they lose out to Bolton in the play-off final.
2002: March 15 - Replaces Walter Smith as Everton manager. Everton win three of their first four matches under his leadership and escape relegation by seven points.
December 5 - With Everton fifth in the Premiership after four successive 1-0 wins in November, Moyes is named Barclaycard manager of the month - the first Everton boss to land such an award for more than three years.
2003: January - Everton suffer surprise 2-1 loss to Third Division Shrewsbury in FA Cup third round.
May - Everton beaten on final day of season by Manchester United and Blackburn take final UEFA Cup place. Moyes named League Managers' Association manager of the year for the first time.
2004: A more difficult season sees Everton narrowly escape relegation but their 5-1 defeat on final day of season sees them finish 17th.
August - Everton sell star striker Wayne Rooney to Manchester United in a deal worth up to £27million.
November 12 - With Everton third in the Premiership after 12 games, Moyes agrees new five-year contract.
2005: May - Everton finish fourth in the Premier League, above city rivals Liverpool, to qualify for the Champions League. Moyes is again named LMA manager of the year.
August - Everton are beaten in Champions League qualifying by Spain's Villarreal.
September - Everton are hammered 5-1 by Dinamo Bucharest and crash out of the UEFA Cup as well.
October - Everton's league form mirrors their European disaster and they sit bottom of the league, resulting in calls for Moyes' head in some quarters.
2006: May - The Toffees stick with Moyes and recover to finish 11th.
2007: May: Steers Everton into the UEFA Cup with a sixth-placed finish.
2008: March 12: The Blues lose on penalties to Fiorentina in the UEFA Cup last 16.
May: Everton finish fifth to qualify for the UEFA Cup again.
September 29: Admits FA charge of improper conduct in relation to an incident against Stoke on September 14.
October 2: Everton crash out of the UEFA Cup in the first round to Standard Liege.
October 14: Signs new five-year contract at Everton.
2009: April - Everton reach the final of the FA Cup with victory over Manchester United, but eventually miss out on the trophy to Chelsea.
2012: Everton finish the 2011/12 season above arch-rivals Liverpool in the Premier League for the first time in seven years.
2013: May 9: Everton announce Moyes will leave the club at the end of the season. United later confirm he will take over as manager on July 1 on a six-year contract.
September 2 - Returns to Goodison to sign Belgium midfielder Marouane Fellaini
September - Suffers first defeat as United boss as Daniel Sturridge gives Liverpool victory at Anfield. Swiftly followed by 4-1 derby loss at Manchester City and 2-1 reverse at home to West Brom.
2014: January 25 - Signs Spain midfielder Juan Mata from Chelsea for £37.1million.
January - FA Cup third-round exit at hands of Swansea is compounded by Capital One Cup defeat to Sunderland, going down on penalties in the semi-final second leg at Old Trafford.
March - Oversees 3-0 home loss to Liverpool, but guides the club into Champions League quarter-finals by overturning 2-0 first-leg deficit against Olympiacos.
April 9 - Moyes' side crash out of Champions League, 4-2 on aggregate against Bayern Munich.
April 20 - United lose 2-0 at Moyes' former club Everton.
April 22 - Sacked by United.