Jose Mourinho’s side were reduced to 10-men late on when Paul Pogba was sent off for a dangerous tackle and they were aided by a stunning goalkeeping display by David De Gea throughout.
But they did telling damage early on when Antonio Valencia pounced on a loose Laurent Koscielny pass to drill the opener, before Jesse Lingard side-footed a second after robbing Shokdran Mustafi to link smartly with Romelu Lukaku and Anthony Martial.
The strikes meant United had scored as many goals in 11 minutes as they had in eight away fixtures against the Premier League’s so-called ‘big six’ clubs.
But an end-to-end first-half, which delivered 20 shots on goal, saw Arsenal hit the woodwork through Alexandre Lacazette and Granit Xhaka during a frenetic goalmouth scramble, before De Gea denied Hector Bellerin, Sead Koasinac, and spectacularly prevented a Lukaku own goal.
The Spaniard could do nothing about Lacazette’s simple finish on 48 minutes but after Lingard had hit the post in a breathless start to the second half, De Gea produced an unbelievable double save from Lacazette and Alexis Sanchez.
His heroics maintained the advantage during an opening 15 minutes to the second half which saw United have just 26% of possession, but Lingard was on hand to tap in a third on 63 minutes after good work by Pogba
Pogba’s mistimed tackle on the back of Bellerin’s leg earned him a straight red card, which means the Frenchman will now miss the Manchester derby next Sunday.
But his moment of woe felt merely a footnote in a riveting encounter which moved second-placed United to within five points of their city rivals.