United came from behind to see off a plucky Middlesbrough side with two goals in the last five minutes to earn a sixth successive win.
The Reds ended 2016 on a high after being frustrated for so long - twice by the woodwork and then by referee Lee Mason who mystifyingly ruled out a perfectly legitimate Zlatan Ibrahimovic goal.
Grant Leadbitter put Boro ahead 20 minutes from time but, with the visitors within sight of a smash-and-grab win, United rallied and finally overhauled the stubborn and resilient Teessiders.
Anthony Martial equalised and Paul Pogba looped home a header to complete a vintage United victory and extend our unbeaten run to 12 games.
Adama Traore went close early on after he had sprung forward on the counter-attack, and Stewart Downing then failed to trouble David de Gea with a shot from distance.
Pogba hit the post with an acrobatic effort from Mkhitaryan's header across goal, but Boro continued to pose a threat.
Another foray forward, led by the impressive Traore, who wriggled away from Daley Blind, saw him cut the ball back for the onrushing George Friend but Marouane Fellaini blocked well.
Then came the main talking point of the half and, as so often this season, it involved a refereeing decision.
After Martial had rattled the post from distance, he collected the loose ball, crossed for Zlatan and the Swede beat former United stopper Victor Valdes to it and stabbed in.
Referee Mason, however, ruled that Ibra had lead with a high foot and Boro's parity remained intact.
Valdes saved well from the Swede after Pogba had picked him out, and the keeper was tested again when he beat out Martial's effort from close range.
United had upped the ante, but then came the sucker-punch on 67 minutes.
A cross from Calum Chambers found Alvaro Negredo who nodded down for the onrushing Leadbitter to side foot home and put the Teessiders ahead against the run of play.
Valdes - who played two games for United under LVG - continued to frustrate his old side when he saved well from Ibrahimovic and then thwarted Martial when the Frenchman was one-on-one.
Martial and United were not to be denied, however, and we dragged ourselves level five minutes from time.
Eric Bailly's long ball was nodded down by Ibrahimovic and Martial ran on to the ball to fire in from ten yards.
A minute later, Old Trafford erupted again as United turned the game on its head and completed a fine come-from-behind win.
Substitute Juan Mata picked out Pogba who looped home a header from 12 yards as United go into 2017 in the highest of spirits.
Overall team performance: 8/10
United Faithful Man of the Match: Anthony Martial