Two goals from Jesse Lingard settled a modern Premier League classic in Manchester United's favour as they survived an Arsenal onslaught and the sending off of Paul Pogba to keep in touch with Manchester City.
Jose Mourinho's side produced a masterclass in counter-attacking football but were indebted to goalkeeper David De Gea for making a succession of crucial saves to keep Arsenal out.
A swift one-two inside the opening 11 minutes had Arsenal floored, as Antonio Valencia's low drive and Lingard's finish from a cute Anthony Martial flick through put United in command.
Arsenal should have scored on several occasions during the first-half but did halve the deficit early in the second courtesy of Alexandre Lacazette.
De Gea made a critical double save from Lacazette and Alexis Sanchez to keep United ahead, before they broke clear to extend their lead through Lingard's second.
Pogba was then sent off for a stamp on the back of Hector Bellerin's knee, meaning he'll miss next weekend's derby with City. But the 10-men of United clung on to move within five points of the leaders.
More to follow.
Antonio Valencia is at the centre of celebrations after opening the scoring for Manchester United in the fourth minute
The United right wing-back drilled home a low shot after Arsenal's defence was pulled out of position by Paul Pogba
Valencia watches as his low shot beats Arsenal goalkeeper Petr Cech and finds the bottom corner for the opening goal
Valencia (right) leads the United celebrations with Paul Pogba and Victor Lindelof after his early strike gave them the lead
Jesse Lingard scores United's second goal on 11 minutes after being slipped through by Anthony Martial's cute flick
Lingard starts to celebrate after seeing his shot beat Arsenal goalkeeper Petr Cech and nestle in the net for the second
Lingard celebrates by showing off some dance moves in front of the travelling Manchester United fans at the Emirates
United's Paul Pogba and Romelu Lukaku are pumped up as they shout to the travelling fans after Lingard's goal
Aaron Ramsey and his Arsenal colleagues look dejected after falling two goals behind in just 11 minutes at the Emirates
Alexandre Lacazette halved the deficit early in the second-half, following in to score after Aaron Ramsey teed him up
United were caught out attempting to appeal for an offside, allowing Ramsey to knock the ball back to Lacazette to score
The goal, on 49 minutes, have Arsenal a lifeline in the match as Lacazette celebrates with his team-mates
David de Gea reacts with dismay after Lacazette finally breaks down United's stubborn defensive resistance
Having been under the cosh for most of the second-half, United broke away to score a third courtesy of Jesse Lingard
Lingard celebrates with a knee slide after scoring his second of the evening and United's third on 63 minutes