Manchester United outclassed Arsenal at the Emirates to maintain the pressure on Premier League leaders Chelsea - and brutally expose Arsene Wenger's title ambitions.
Sir Alex Ferguson's champions unleashed a devastating display of sweeping, counter-attacking football inspired by the brilliance of Wayne Rooney and Nani.
Wenger had outlined the importance of the meeting with United in the context of the battle to win the Premier League, and by the final whistle saw his hopes placed in painful perspective by a masterful United.
United now stand only one point behind Chelsea having played a game more, but the manner of this victory will send out the message that no-one will find it easy to wrest the title away from Ferguson's side.
Nani, so long a figure of frustration at Old Trafford, has rarely performed with more threat and finesse than he did in the first 45 minutes here as he ran Gael Clichy ragged and ensured United had established a two-goal lead by the interval.
He baffled Arsenal with a stunning piece of trickery that forced uncertain Arsenal keeper Manuel Almunia to turn his cross into his own net after 33 minutes and then set up Rooney's 100th Premier League goal four minutes later.
United caught Arsenal cold as they turned defence into attack, Rooney sprinting from just outside his own area to take a return pass from Park and finish in style.
Ji-Sung Park graphically illustrated the gulf between Arsenal and United just after half-time when he took advantage of a path lack of resistance to run unchallenged from inside his own half to beat Almunia.
Thomas Vermaelen's deflected shot late on set up an Arsenal rally of sorts, but the scoreline barely reflects United's superiority as they gave the Gunners a painful lesson in ruthless, cutting edge football.
United boss Ferguson opted for Nani ahead of £15m summer signing Antonio Valencia - and the success of the decision was probably beyond all his expectations as the Portuguese winger tortured Arsenal.
Andrey Arshavin offered early optimism for Arsenal's fans with a couple of trademark twisting runs and shots off target - but they turned out to be a false dawn as United soon moved into a different class to Arsenal.
William Gallas needed to make timely interventions as United's crisp passing threatened to carve United open, with Nani the primary source of danger as he proved simply too fast and too clever for Clichy.
And when Nani helped fashion United's opener after 33 minutes, it was the signal for a blistering passage of play that saw Arsenal's hopes of getting anything from such a crucial game disintegrate.
Nani tricked his way past Cesc Fabregas into the area with sleight of foot worthy of his celebrated former United team-mate Cristiano Ronaldo, although Almunia should have done a lot better than palm the ball in with a feeble attempt at clearance.
United topped that for quality four minutes later with a goal that, for Arsenal, bore the grim hallmarks of Ronaldo's third goal in the Champions League semi-final second leg at The Emirates last season.
Rooney, not far from the edge of his own penalty area, released the rampaging Nani down the right-flank, and arrived at the other end of the pitch on cue to drill a low finish past Almunia and send Ferguson out of his technical area and along the touchline in sheer delight.
Nani should have made it three when Rooney found him unmarked at the far post, but his goalbound shot took a crucial touch of Vermaelen that went undetected by referee Chris Foy and flew wide.
If Arsenal had any hope of mounting a fightback they were emphatically snuffed out seven minutes after the interval in a manner that would have been as embarrassing for Wenger as it was satisfying for Ferguson.
Park ran from just inside his own half, free from any Arsenal challenge, and accepted what was almost an open invitation to slip the simplest of finishes past the exposed Almunia.
Vermaelen gave the discontented Arsenal fans a moment of cheer after 80 minutes when his shot was deflected out of the reach of Edwin van der Sar by Jonny Evans - and there were even further opportunities to set up the unlikely prospect of a thrilling finale.
Gallas headed wide of an open goal and Vermaelen saw a shot blocked by Patrice Evra, but Rooney displayed a rare moment of fallibility by wasting the opportunity to give the score a more realistic appearance, shooting wide in stoppage time.