Norwich recorded only their second win over Manchester United in 15 league matches thanks to a brilliant headed goal from Anthony Pilkington.
The ex-Huddersfield forward struck 30 minutes from time when he flicked in Javier Garrido's cross from the left.
United, who had been usurped at the top of the table by rivals City coming into the game, looked well below their best.
Ferguson praises goalkeeper John Ruddy
Ashley Young's shot was saved by John Ruddy, who also tipped over a header from his own player Sebastien Bassong.
The England goalkeeper would have expected a busier evening, but both he and his team witnessed a flat performance from the visitors.
Although the 19-time champions have bounced back from such setbacks many times, what might be of concern to manager Sir Alex Ferguson is their lack of creativity from midfield, particularly from the centre.
In a flat 4-4-2, Ryan Giggs was ineffective, bar one deft ball over the top. And bringing on Paul Scholes, who turned 38 this week, was a clear sign of their lack of depth in this area.
Nonetheless, they came into the fixture in good form, with nine wins from their previous 10 league fixtures.
But Norwich, who had kept three clean sheets in their last four league outings, were certainly not going to lie down.
While another shutout seemed a step too far for the Canaries against a trigger-happy strikeforce of Robin van Persie and Javier Hernandez, the home defence showed that their recent improvement was no flash in the pan.
Steve WilsonBBC Match of the Day commentator
"One of the greatest results in Norwich City's recent history.
"A wonderful goal from Anthony Pilkington, a wonderful result for Norwich City and a fantastic performance from John Ruddy.
It was a red letter day as they beat the Red Devils."
Norwich manager Chris Hughton mentioned prior to the match that fielding the same centre-back pairing in recent weeks had helped his side's performances and neither Bassong nor Michael Turner let him down.
Turner was particularly impressive, consistently getting in front of his man Hernandez to clear.
In fact, during that first half United managed to get behind the Canaries backline only on a handful of occasions - and only once did they give the home side the jitters.
That chance for last season's runners-up was conjured up shortly before half-time when Giggs floated a pass into the area which Van Persie allowed to drop over his shoulder. But the Netherlands international made a mess of his footwork, much to the amusement of the home support.
Norwich created the best opportunities during the opening period with former Leeds forward Robert Snodgrass flicking a header a fraction wide before narrowly failing to get a connection on Pilkington's driven cross.
The Canaries seemed to have the freedom of the wings to cross the ball into the United area, although rarely did they pose problems for Chris Smalling and Rio Ferdinand - that was until the 60th minute.
Spaniard Garrido, on loan from Lazio, once again took advantage of the space afforded to his side out wide and delivered a flat-flighted ball into the area which Pilkington beautifully guided past the reach of Anders Lindegaard.
Norwich win over Manchester United very special - Chris Hughton
It was 11th time in 18 matches that United had fallen behind this season - but they had won 15 points in the league having been in losing positions.
Ferguson brought on forward Danny Welbeck, who scored for England in midweek, and veteran Scholes with 20 minutes remaining.
Welbeck threatened on a couple of occasions, but the closest the visitors came to escaping with a point in the closing stages was when Bassong inadvertently forced Ruddy to tip his header over the bar.
Late in the game, Jonny Howson had a chance to add a second for Norwich, but he messed up his lines after being put clean through.
Luckily for him there was no late heartache for his team, who climb to 13th in the table.
90:00+5:08 The final whistle is blown by the referee.
90:00+4:39 Drilled left-footed shot by Oliveira Anderson. Save made by John Ruddy.
90:00+3:49 Close range header by Chris Smalling goes wide of the left-hand post.
90:00+3:28 Corner taken by Ryan Giggs, Sebastien Bassong makes a clearance.
90:00+2:52 Javier Garrido challenges Ashley Young unfairly and gives away a free kick. Robin van Persie crosses the ball in from the
free kick, clearance made by Sebastien Bassong.
90:00+1:47 Booking Rafael Da Silva receives a caution for dissent.
90:00+0:39 Substitution Elliott Bennett replaces Robert Snodgrass.
89:19 Effort from the edge of the penalty area by Jonathan Howson goes wide of the left-hand post.
89:08 Michael Carrick has a drilled shot. Blocked by Bradley Johnson.
88:14 Paul Scholes crosses the ball, save by John Ruddy.
87:43 Shot from 20 yards by Anthony Pilkington. Comfortable save by Anders Lindegaard.
86:19 The ball is swung over by Steve Morison.
85:52 Centre by Ashley Young, save by John Ruddy.
83:15 Steve Morison concedes a free kick for a foul on Rafael Da Silva. Ashley Young takes the direct free kick.
82:09 Substitution Rio Ferdinand leaves the field to be replaced by Oliveira Anderson.
82:09 Substitution Jonathan Howson comes on in place of Wesley Hoolahan.
82:09 Substitution Steve Morison on for Grant Holt.
81:36 Ashley Young sends in a cross, clearance made by Steven Whittaker.
80:10 Corner taken by Ashley Young played to the near post, clearance made by Grant Holt.
79:46 The ball is crossed by Ryan Giggs, clearance made by Sebastien Bassong.
78:33 Foul by Patrice Evra on Robert Snodgrass, free kick awarded. John Ruddy takes the direct free kick.
78:14 Centre by Ashley Young, Javier Garrido makes a clearance.
75:19 A cross is delivered by Rafael Da Silva, Danny Welbeck takes a shot. Save made by John Ruddy.
74:59 Inswinging corner taken by Robin van Persie from the left by-line, save by John Ruddy.
73:58 Robert Snodgrass crosses the ball.
73:10 Rafael Da Silva gives away a free kick for an unfair challenge on Bradley Johnson. The free kick is swung in left-footed by
Javier Garrido, Robin van Persie makes a clearance.
68:41 Inswinging corner taken left-footed by Robin van Persie, Robert Snodgrass manages to make a clearance.
68:41 Substitution Javier Hernandez goes off and Danny Welbeck comes on.
68:41 Substitution Paul Scholes joins the action as a substitute, replacing Antonio Valencia.
67:58 The ball is swung over by Ryan Giggs, clearance made by Anthony Pilkington.
67:15 Foul by Robert Snodgrass on Chris Smalling, free kick awarded. Rio Ferdinand takes the free kick.
63:58 Javier Hernandez challenges Bradley Johnson unfairly and gives away a free kick. Free kick taken by Javier Garrido.
61:42 Bradley Johnson delivers the ball.
61:31 The ball is delivered by Anthony Pilkington, Rio Ferdinand makes a clearance.
61:12 Grant Holt takes a shot. Rio Ferdinand gets a block in.
59:15 Assist on the goal came from Javier Garrido.
59:15 GOAL - Anthony Pilkington:Norwich 1 - 0 Man Utd Anthony Pilkington grabs a headed goal from inside the penalty area. Norwich 1-0 Man Utd.
58:39 Rafael Da Silva takes a shot. Blocked by Bradley Johnson.
58:10 A cross is delivered by Antonio Valencia, Alexander Tettey makes a clearance.
56:07 Anthony Pilkington delivers the ball.
55:25 Anthony Pilkington is ruled offside. Antonio Valencia takes the free kick.
54:23 Bradley Johnson fouled by Javier Hernandez, the ref awards a free kick. The free kick is delivered right-footed by Anthony
Pilkington from left wing, Rafael Da Silva makes a clearance.
53:39 Javier Garrido delivers the ball.
52:58 Anthony Pilkington sends in a cross, Rio Ferdinand makes a clearance.
49:21 Foul by Patrice Evra on Robert Snodgrass, free kick awarded. The free kick is swung in left-footed by Robert Snodgrass, clearance
made by Rafael Da Silva.
47:45 Inswinging corner taken by Robin van Persie from the right by-line played to the near post, clearance by Steven Whittaker.
46:52 Robin van Persie takes a shot. John Ruddy makes a save.
46:11 Centre by Antonio Valencia, save by John Ruddy.
45:01 The second half kicks off.
45:00+1:06 It is the end of the first-half.
45:00+0:54 The ball is sent over by Steven Whittaker, save made by Anders Lindegaard.
44:20 Ashley Young gives away a free kick for an unfair challenge on Robert Snodgrass. Robert Snodgrass crosses the ball from the
free kick left-footed from right wing, clearance made by Rafael Da Silva.
42:38 Corner taken by Robin van Persie, save by John Ruddy.
Correction - 42:16 Drilled right-footed shot by Chris Smalling. Grant Holt gets a block in.
42:16 Chris Smalling produces a drilled right-footed shot from 12 yards. Grant Holt gets a block in.
42:04 Robin van Persie takes a inswinging corner from the right by-line played to the near post, Steven Whittaker makes a clearance.
41:45 Ashley Young has a drilled shot. Save made by John Ruddy.
41:15 Inswinging corner taken left-footed by Robin van Persie from the right by-line to the near post.
38:19 The assistant referee signals for offside against Javier Hernandez. Free kick taken by John Ruddy.
37:55 Robert Snodgrass crosses the ball, Chris Smalling makes a clearance.
37:01 Rafael Da Silva produces a cross, save by John Ruddy.
35:56 Michael Carrick fouled by Grant Holt, the ref awards a free kick. Direct free kick taken by Michael Carrick.
30:57 Shot by Alexander Tettey from 35 yards. Anders Lindegaard makes a comfortable save.
30:30 Bradley Johnson produces a cross, save by Anders Lindegaard.
29:17 The offside flag is raised against Grant Holt. Rio Ferdinand takes the indirect free kick.
28:52 Bradley Johnson takes a shot. Chris Smalling gets a block in.
28:06 Javier Hernandez gives away a free kick for an unfair challenge on Michael Turner. John Ruddy takes the direct free kick.
27:09 The ball is delivered by Antonio Valencia.
24:53 Javier Garrido crosses the ball.
23:10 Robert Snodgrass produces a header from deep inside the six-yard box which goes wide of the right-hand post.
20:02 Corner taken right-footed by Ashley Young from the right by-line, Headed effort on goal by Patrice Evra from inside the penalty
box misses to the right of the target.
19:21 Unfair challenge on Ashley Young by Wesley Hoolahan results in a free kick. Free kick taken by Ashley Young.
17:01 Shot by Wesley Hoolahan. Comfortable save by Anders Lindegaard.
14:28 Shot by Ashley Young from 30 yards. Save by John Ruddy.
13:46 Michael Turner challenges Javier Hernandez unfairly and gives away a free kick. Direct free kick taken by Ashley Young.
13:29 Grant Holt concedes a free kick for a foul on Rafael Da Silva. Direct free kick taken by Michael Carrick.
13:12 The ball is swung over by Ashley Young, Michael Turner makes a clearance.
11:43 Michael Carrick fouled by Grant Holt, the ref awards a free kick. Direct free kick taken by Michael Carrick.
10:37 A cross is delivered by Anthony Pilkington, clearance made by Rio Ferdinand.
8:52 Foul by Steven Whittaker on Ashley Young, free kick awarded. Ryan Giggs sends in a cross, Effort from the edge of the box
by Robin van Persie goes wide of the left-hand upright.
7:40 Anthony Pilkington has an effort at goal from the edge of the box that misses to the right of the target.
6:58 Inswinging corner taken right-footed by Ashley Young, John Ruddy makes a save.
4:40 Shot from just outside the area by Robert Snodgrass misses to the right of the target.
3:01 Ashley Young takes a inswinging corner from the left by-line played to the near post, clearance made by Grant Holt.
2:44 Inswinging corner taken by Ashley Young from the left by-line, clearance by Steven Whittaker.
2:27 Robin van Persie takes a shot. Save by John Ruddy.
1:05 Anthony Pilkington is caught offside. Rafael Da Silva takes the free kick.
0:41 Foul by Grant Holt on Patrice Evra, free kick awarded. Free kick taken by Ryan Giggs.
0:00 The game begins.
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