Old Trafford literally was the Theatre of Dreams for wonderful, warrior-like West Ham as the Manchester United nightmare continued for Sir Alex Ferguson.
Jermain Defoe's 64th minute header gave Hammers a deserved first league win at the home of the champions since August 1986, while the Red Devils' sixth defeat of the season saw them slump down to ninth place, 11 points off leaders Liverpool and almost certainly out of the title race.
After securing that last-gasp draw against Aston Villa in midweek, West Ham had come into this tough test unchanged, while confident United made three switches from the side that had so comprehensively seen off Boavista in the Champions League.
Young defender John O'Shea plus Ole Gunnar Solskjaer and Luke Chadwick came in for Laurent Blanc, eleven-goal Ruud Van Nistelrooy and £28million Juan Sebastien Veron following the Reds' 3-0 victory over the Portuguese champions.
Replicating Sir Alex Ferguson's 4-4-2 line-up, Glenn Roeder did tinker with his midfield as Trevor Sinclair and Don Hutchison took respective wide left and right berths, while the youthful flair of Joe Cole and Michael Carrick were asked to stand toe-to-toe against Roy Keane and Nicky Butt. And, like the entire West Ham side, they did not disappoint.
Certainly, the Hammers gave as good as they got during an opening first period that saw most of the activity taking place in the United half. Indeed, on 15 minutes Defoe came within a whisker of silencing Old Trafford as Fabien Barthez plucked Sebastien Schemmel's cross off his head and then the under-fire French 'keeper was forced to palm away Paolo Di Canio's low 25-yarder for the first corner of the game.
Butt's frustrated scyth on the fleeing Cole earned the midfielder the first of eight yellow cards dispatched by referee Durkin, before Dwight Yorke and Keane lashed angled shots into the side-netting and David James produced the first of several fine stops by acrobatically clawing Scholes' 20-yarder out from under his right-hand angle.
Midway through the half, another crude lunge on Defoe then brought bookings for O'Shea and the protesting Keane to the disgust of the restless home support, who then saw an unmarked Sinclair send an overhead kick sailing over.
With the hard working Hammers still high on confidence, Schemmel then drilled Cole's sliced shot across the face of goal, prior to being cautioned for tripping Chadwick, but as United finally started to threaten in the closing stages, James kept it goalless, by bravely plucking the ball off Yorke's studs prior to fisting out Scholes' screamer and holding Butt's ten-yard volley.
Emerging for the second half, a more urgent United looked a totally different proposition as the soaring Scholes soon glanced Solskjaer's corner across the face of goal before volleying into the side-netting from the edge of the box, and after surviving vociferous cries against him for handball, Hutchison was then yellow-carded for felling Scholes.
While substitute David Beckham waited to make a grand entrance, the slippery Solskjaer forced James to save his low six-yarder as the roof looked all set to cave in on a dogged Hammers defence coming increasingly under pressure.
But, incredibly, the Red tide was turned when the visitors' first real attack of the half saw them take the lead on 64 minutes as Cole played in the overlapping Di Canio whose deep, looping cross was nodded home at the far post by Defoe.
While the celebrations of the ecstatic east enders mirrored those of last January's epic FA Cup win, the United response saw Scholes booked for chopping Carrick, while Andy Cole replaced Butt and Mikael Silvestre's header forced James into yet another brilliant full-length save.
An unpunished body check on Di Canio brought a yellow card for the irate Italian and after Gary Neville joined him in the book for upending Defoe, the Hammers' goal-scoring hero was then replaced by Titi Camara for a predictably frantic final ten minutes that saw an invincible James repel everything that United - including rush-goalie Barthez - could throw at him as Hammers held on for a memorable victory.
6 - Butt's dangerous cross from the left is cleared well by Dailly.
9 - Joe Cole has a speculative 25-yard shot charged down by a defender.
14 - Schemmel whips in a cross from the right that is held by Barthez.
17 - Di Canio's fierce drive from the edge of the area is tipped round the post by Barthez.
18 - Butt booked for a foul on Cole.
21 - Silvestre turns Carrick in the area but fires his shot into the side-netting.
23 - Scholes collects the ball in space and unleashes a powerful drive that is destined for the top corner until James brilliantly tips it round the post.
25 - O'Shea booked for foul on Defoe.
25 - Keane booked for dissent.
29 - Di Canio's chip beats the offside trap and finds Sinclair in space but the midfielder hastily lashes a first-time volley over the bar.
35 - Cole finds Sinclair, whose shot is deflected wide for a corner.
36 - Cole's miscued shot falls kindly to Schemmel, whose fierce drive whistles just inches wide of the far post.
40 - Schemmel booked for a foul on Chadwick.
42 - Scholes shot is well parried by James and then cleared by Cole.
Added time: 2 minutes.
Half-time: Manchester United 0 West Ham 0.
49 - Solskjaer's corner is headed just wide by Scholes from eight yards out.
51 - Di Canio's dangerous cross from the left is narrowly missed by Hutchison.
55 - Hutchison booked for a foul on Scholes.
59 - Substitute for Manchester United, Beckham replaces Chadwick.
59 - Beckham's cross is headed wide by Yorke.
60 - Di Canio releases Sinclair on the left but the England man's defence-splitting pass finds Defoe in an offside position.
64 - GOAL! Hammers take a deserved lead as excellent work by Cole finds Di Canio on the left.. The Italian cuts inside before delivering a deep cross that is met by Defoe, who powers his header past Barthez. Manchester United 0 West Ham 1.
65 - Scholes booked for foul on Carrick.
68 - Substitute for Manchester United, Andy Cole replaces Butt.
73 - James pulls off a superb save from Silvestre's close range header.
74 - From Beckham's cross, Solskjaer's header is again kept out by James.
76 - Di Canio booked for dissent.
81 - Substitute for Manchester United, Fortune replaces Yorke.
82 - Gary Neville booked for foul on Defoe.
83 - Substitute for West Ham, Camara replaces Defoe.
85 - Beckham's free-kick sails just wide of the far post.
89 - Silvestre's low cross is bravely held by James.
Added-time: 4 minutes.
Full-time: Manchester United 0 West Ham United 1.