Demba Ba scored his 15th goal of the season in fine style, Yohan Cabaye struck a perfect free-kick and Phil Jones scored a calamitous own-goal to enable the Toon to score their first victory over the Red Devils since September 2001.
The three points allowed Alan Pardew's men to go within one of Liverpool to remain seventh as Sir Alex Ferguson's United fell one win behind neighbours and league leaders Manchester City with their second defeat on the trot following the shock 3-2 loss to Blackburn Rovers on New Year's Eve.
Newcastle had played with a very positive lilt and managed to take the lead in the 33rd minute when a long ball from Tim Krul was flicked on by the head of Shola Ameobi for Demba Ba. The Senegalese hooked a brilliant first-time shot over his left shoulder on the volley and into the corner to be the first player to score past Anders Lindegaard in the Premier League and just the fourth player to breach the Manchester defence away from home this season.
Just over two minutes after the break, Newcastle were two to the good when Ba won a free-kick outside the area which Yohan Cabaye expertly curled into Lindegaard's top right corner from about 25 yards from a fairly central position.
Late in the contest, Newcastle were gifted a third when Krul sent another long ball deep into attack where Phil Jones and Lindegaard had a complete mix up which ended in the young defender deflecting into his own goal much to the delight of the vocal Toon army.
Earlier, Ba should have made contact with Danny Simpson's cross moments before Cabaye tested Lindegaard with his left-footed attempt. Cheick Tiote then forced another straightforward save from the Dane with a very long range attempt in the eighth minute.
The 11th minute saw Krul keep out a firmly struck Nani attempt from the edge of the area with his palmed stop falling into the path of Wayne Rooney who was unable to get there in time for a killer touch a few minutes before Dimitar Berbatov's deflected header beat the Magpies keeper but not the far upright in a very close call for the visitors.
Newcastle had big calls for a penalty in the 25th minute when Rio Ferdinand clashed with Ba in the area but referee Howard Webb waved away the Toon protests.
The best other chances came when Newcastle's RyanTaylor curled his free-kick just over Lindegaard's crossbar in the 44th minute prior to Ba hitting a devil of a bouncing shot at the Danish keeper.
Man Utd should have got one back just prior to the hour-mark when Nani crossed for substitute Danny Welbeck who flicked on for Rooney but Simpson was well-placed on the goal-line to snuff out the advances of the visitors.
For Manchester, 2012 has started just as 2011 ended - with defeat - and Ferguson will be at his most vociferous at training this week whilst it is cheers and jubilation for Pardew's charges who will have to deal without Ba and Tiote who are now off to the African Cup of Nations for possibly a month.
TRIBAL ASKS: Is it back to the drawing board for Man Utd after conceding six in two? Does Fergie need a defender or is it simply a glitch? On the other hand, what will Newcastle do without Ba?
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