Robin van Persie downed old club Arsenal to blast Manchester United back into the Premier League title race as David Moyes enjoyed his biggest win as Red Devils manager.
Van Persie rose unchallenged to guide home Wayne Rooney's 27th-minute corner to spark scenes of jubilation at Old Trafford and silence the taunts of the visiting fans.
On another amazing weekend, in which Chelsea's home draw on Saturday was followed within 24 hours by shock defeats for Tottenham and Manchester City, United have now closed to within five points of Arsenal, who suffered their first league defeat since the opening day of the season.
Indeed, six points now separate the first eight in the table, with Liverpool and Southampton now Arsenal's closest pursuers.
United deserved their triumph too.
Quite apart from Van Persie's goal, Rooney ran himself to a standstill and Phil Jones was immense, initially in midfield, then central defence following the departure of Nemanja Vidic with a head injury.
The hosts owed a debt of thanks to Chris Smalling too.
Smalling might have wasted an outstanding chance to seal victory when he failed to get a proper connection to Van Persie's deep free-kick and headed disappointingly wide.
But, just as Olivier Giroud was lining up a shot from an excellent position inside the United box, it was Smalling who stepped in to make the decisive tackle and preserve United's unbeaten home record against the Gunners that stretches back to 2006.
There was no real surprise Van Persie should return to the United starting line-up, still less the Dutchman celebrated the opener with intent.
The trend has been for players to merely acknowledge what they had done, rather than glory in the pain they had caused to their old club.
Van Persie refrained himself when he scored in the corresponding fixture last term.
However, the vicious taunts aimed at him by the visiting contingent throughout the opening stages at Old Trafford evidently changed his stance.
For Van Persie raced away in glee as his header flew over Kieran Gibbs before he was submerged by team-mates, then adopting a clenched fist salute as he re-appeared.
The blame for Van Persie's goal seemed to be pinned on Aaron Ramsey, who moved away from his station as Rooney delivered the corner.
There had to be some culpability as it was surely not part of Arsene Wenger's game-plan to afford such a predatory striker so much room.
It was not the only issue for Wenger to address at half-time.
Since that shock opening-day defeat to Aston Villa, that first period was as bad as Arsenal have been.
Missing Per Mertesacker due to a virus that was also affecting Mikel Arteta, the Gunners lacked the zip that has taken them clear at the Premier League summit.
Only Mathieu Flamini escaped the malaise, and he was booked for a late tackle on Jones.
The young England star was one of United's stand-out performers, driving out of midfield in a manner so obviously lacking for the past three seasons.
He was also at the centre of the first of two worrying head clashes.
Cautioned when he clattered into Wojciech Szczesny, TV replays showed the contact to be accidental.
For a few seconds, the Arsenal keeper did not move.
After treatment, Szczesny continued, as did Jones, who had moved away rubbing his head.
Nevertheless, given the recent furore over Hugo Lloris, the decision raised an eyebrow.
In the final seconds of the opening period, Vidic went down in a heap after his face was crunched by David de Gea's knee.
There was no immediate substitution as United reached the interval with 10 men.
The tough-tackling Serbian did not return for the second period though as Moyes introduced Tom Cleverley and moved Jones back into central defence.
It all rather obscured a disappointing lack of goalmouth action.
Szczesny had earlier saved a long-range effort from Rooney but Arsenal were devoid of opportunity as Olivier Giroud failed to find any space and Mesut Ozil struggled to make an impact.
The visitors improved after the break, with Ozil slicing an angled effort into the side-netting.
Wenger still felt compelled to introduce Jack Wilshere after an hour, a move that came just after his side had survived Rooney nipping past Bacary Sagna and belting a low shot inches wide.
The visitors pushed forward in increasing desperation. But United defended valiantly.
Smalling was involved in key moments at both ends before Sagna's low cross bounced inches away from Nicklas Bendtner.
David De Gea: Commanding at crosses and not afraid to come forward, but his shot-stopping ability was not tested. 6/10.
Chris Smalling: Said to be the weak link in the United defence by some but got through untroubled. 6.
Nemanja Vidic: Looked in little difficulty until he was forced off after a nasty clash of heads with De Gea just before half-time. 6.
Jonny Evans: Also not put under great strain by Arsenal but cleared effectively when required. 6.
Patrice Evra: Made some dangerous runs down the left as United forced the pace. 7.
Phil Jones: Made some good bursts from midfield and looked strong before a reshuffle saw him move into defence, where he was also solid. 8.
Michael Carrick: Kept United moving forward from midfield in his usual efficient manner. 7.
Antonio Valencia: Appeared to drift in and out of the game and was not a potent force out wide. 6.
Wayne Rooney: Tireless and showed all his usual hunger to continually trouble Arsenal. Delivery for Van Persie's goal was superb but spurned good chance himself. 9.
Shinji Kagawa: Hard-working display, looking to spark attacks but unable to really impress. 7.
Robin van Persie: Appeared to have little service for the most part but that mattered little as he ghosted in at the right time to head home. 7.
Tom Cleverley (for Vidic, 46): Did not provide the midfield steel Jones did before the break and Arsenal began to gain more possession. 6.
Ryan Giggs (for Kagawa, 78): Brought fresh legs and a calming influence late on. 6.
Marouane Fellaini (for Van Persie, 85): Kept things steady as United secured a fine win. 6.
Wojciech Szczesny: Bravely continued after clash of heads with Jones but not hugely tested. 6.
Bacary Sagna: Grew in influence in the second half, making a vital clearance and whipping in a dangerous cross. 7.
Laurent Koscielny: Looked to be keeping tight to Van Persie early on and generally stood firm but fingers could be pointed across the whole defence over the former Gunners striker's goal. 6.
Thomas Vermaelen: Kept busy by Rooney throughout and the defensive line was strong, one moment aside. 6.
Kieran Gibbs: Could not keep out Van Persie's header despite being positioned on the line but offered a threat in attack. 6.
Mathieu Flamini: One of the more influential members of the Arsenal side, winning possession and looking to move things forward. 7.
Mikel Arteta: Played some nice balls but unable to influence greatly from a deep role. 6.
Aaron Ramsey: Took up some good positions but United kept a close eye on Arsenal's man of the moment, restricting his influence. 6.
Mesut Ozil: Below his usual standard. Despite improving in the second half, the German was sometimes caught in possession and misplaced passes. 6.
Santi Cazorla: Particularly quiet in the first half, the Spaniard came deep to get involved but was also guilty of giving the ball away. 6.
Olivier Giroud: Was also more of a threat up front in the second half after struggling before the break. 7.
Jack Wilshere (for Flamini, 61): Replaced Flamini as Arsenal sought more creativity but did not seem to be up with the pace of the game. 6.
Nicklas Bendtner (for Cazorla, 78): Provided fresh impetus up front but unable to make an impression. 5.
Serge Gnabry (for Arteta, 83): Got some good possession out wide and looked dangerous but his introduction was perhaps too late. 6.