For the first time in his 13th attempt, Arsene Wenger guided Arsenal to victory against a Jose Mourinho managed team in the Premier League.
The Gunners entered the game off the back of a disappointing North London derby defeat, whilst Man Utd's mid-week European exploits saw them edge past Celta Vigo en route to a Europa League final.
Second half goals from Granit Xhaka and ex-United forward Danny Welbeck secured all three points for Arsenal, in what was at times a tense affair.
Cagey first half, decisive second
The first half was largely uneventful, particularly for a fixture which has so often produced fireworks.
The match had an 'end of the season' feel to it, with both teams on the brink of cup success despite underwhelming league campaigns.
Arsenal midfielder Aaron Ramsey made a promising start to the game, and had a chance to break the deadlock inside the 9th minute. Alexis Sanchez played the Welshman in with a lovely weighted through ball, but Ramsey's effort toward the bottom corner could only force a smart save from David De Gea.
It wasn't until the 54th minute in the second half when Arsenal took the lead, via a fortuitous strike from Xhaka. The Swiss international collected the ball in space and launched an ambitious shot toward goal, the ball took a wicked deflection off Ander Herrera and looped in.
Three minutes later, the hosts doubled their lead. A pinpoint cross by Alex Oxlade-Chamberlain was met by Welbeck who nodded home against his former club. A decisive three minutes in the second half saw Arsenal emerge victorious over United at home for the second season running.
When asked about his thoughts on what was a big win, Arsene Wenger said; "It was important because we lost at Tottenham - that didn’t happen many times. Overall, you play Man United and it’s another big game. We couldn't afford to lose today."
He added; "The first goal was a bit lucky, the second goal was a great goal. I’m happy for Danny as well. When you play centre forward you know you want goals and so it hopefully gives him confidence."
Can Arsenal make the top four?
Arsenal's win over Man Utd sees them remain in 6th position on 63 points. They do however have a game in hand on fourth-placed Manchester City, who are currently on 69 points. Incidentally, The north-Londoners also have two games in hand on third-placed Liverpool, who are on 70 points.
Despite the very real possibility of Arsenal once again ending the season in the top four, Arsene Wenger acknowledges that destiny is not yet in The Gunners' hands.
"We still have a mathematical chance." Said the Frenchman, "all is not perfect but I think we are a bit more defensively focused at the moment than we were a few weeks ago and it helps us a little bit."
Next up for Arsenal is a visit to St. Mary's to take on Southampton. Arsenal supporters will no doubt be hoping for another win as they look to increase the pressure on the sides above them.