United may have had top-scorer Cristiano Ronaldo sitting in the stands, but they had another Portuguese star in Nani to inspire them to this memorable victory.
The 21-year-old winger produced skills right out of the Ronaldo textbook, although this was a night when nothing went wrong for the Red Devils and nothing went right for Arsenal.
If a 4-0 mauling was not bad enough, Arsenal also had Emmanuel Eboue sent off for a 49th minute foul on Patrice Evra when his attempted tackle caught the Frenchman in the stomach.
For United the treble remains a goal, although they will have to motor to overhaul the Gunners' five-point lead at the top of the Premier League.
Arsenal visit Old Trafford in the league in mid-April - another red letter day for England's top two sides.
Wayne Rooney, returning after missing his side's abysmal performance in last Sunday's Manchester derby through suspension, led the United line with a swagger and style and Arsenal's defence a merry dance.
His never-say-die attitude caused Arsenal central defenders Kolo Toure and William Gallas the most painful of headaches and it was Rooney who put United ahead in the 16th minute.
Nani's corner to the near post came off the head of Arsenal striker Nicklas Bendtner to Anderson lurking on the edge of the box.
The Brazilian easily beat Cesc Fabregas to head the ball goalward and Rooney nodded it into the roof of the net from six yards.
United extended their lead four minutes later.
Anderson found Nani on the left and his cross to the near post was headed in by Darren Fletcher from six yards, although the ball brushed Gallas on its way into the net.
Fletcher, enjoying his best ever game for United, was inspirational and created good chances for Rooney and Ji-Sung Park.
But it was Nani who supplied the all-important third goal in the 38th minute.
Michael Carrick's glorious 60-yard pass found Nani in the Arsenal penalty area. The United winger wrong-footed Armand Traore as he took the ball down with his right foot and tucked his shot beyond Arsenal goalkeeper Jens Lehmann and into the net from 12 yards.
United continued to dominate after the break as Arsenal seemed incapable of raising their game and it was fitting that Fletcher should complete the scoring in the 74th minute.
Nani wrong-footed Justin Hoyte before providing a pinpoint cross from the left byline to the far post where Fletcher rose to head home.