Arsenal have moved to within two points of Manchester United in the Premier League table after recording a 2-0 win over the Red Devils at the Emirates Stadium on Sunday afternoon.
Granit Xhaka's deflected effort sent Arsenal ahead in the 54th minute, before Danny Welbeck netted a second three minutes later as Arsene Wenger finally overcame a Jose Mourinho team in the Premier League.
Xhaka started for Arsenal despite initially being ruled out of the clash with a calf problem, while there were also spots for Rob Holding and Welbeck as head coach Wenger went for a 3-4-3 formation once again.
As for Man United, Mourinho made eight changes to the team that started against Celta Vigo on Thursday night, with only Matteo Darmian, Ander Herrera and Henrikh Mkhitaryan keeping their spots in the XI.
There were returns for Chris Smalling, Phil Jones and Juan Mata following injury, while young defender Axel Tuanzebe made his Premier League debut on the right side of the away team's defence.
Man United had a half-chance inside three minutes when Rooney met a brilliant cross from Mata, but the Englishman's header just missed Petr Cech's crossbar as the visitors survived a dangerous moment early on.
Two minutes later, the Red Devils had another opportunity when Rooney fed the dangerous Martial inside the Arsenal box, but the France international could not find a route past Cech at his near post.
Arsenal's first clear chance arrived in the ninth minute when Aaron Ramsey found space inside the Man United box before looking to pick out the bottom corner, but David de Gea was on hand to make a stunning save during an end-to-end period of the match.
Martial's pace continued to cause the home side all sorts of problems as the first period developed, although Arsenal were dangerous when Welbeck had the opportunity to isolate Jones and Smalling in a forward position, and the former Man United youngster had a goal-bound strike just blocked in the 26th minute.
Arsenal twice came close to taking the lead in the 30th minute, but Welbeck saw a powerful strike blocked behind by Smalling, before De Gea kept out a long-range effort from Alex Oxlade-Chamberlain.
Man United then had a wonderful chance after Nacho Monreal's loose back-pass fell to Rooney inside the Arsenal box, but the Red Devils captain could not find a route past Cech from close range as the score somehow remained goalless.
Neither manager looked to their bench at the half-time break, but with the likes of Marcus Rashford, Paul Pogba, Olivier Giroud and Theo Walcott in reserve, there were attacking options for both Mourinho and Wenger to consider.
After a slow start to the second period, Arsenal made the breakthrough in the 54th minute when a long-range strike from Xhaka took a big deflection off the back of Herrera and ended up in the top corner of the net.
Man United just could not respond in the period that followed, and Arsenal scored a second less than three minutes later when Welbeck headed a brilliant Oxlade-Chamberlain cross past De Gea with help from the underside of the crossbar.
Jesse Lingard for Mkhitaryan was the away side's first change of the match just past the hour, before Rashford came off the bench three minutes later as Mourinho looked to hit back in the final 30 minutes of action.
Rooney came close to finding the bottom corner with a 30-yard free kick in the 64th minute, but Cech made a smart save during a period where the away side were firmly on the front foot.
Rooney had another sight of the Arsenal goal in the 75th minute after finding a yard of space in a forward position, but the 31-year-old missed the post with a curling effort as the score remained 2-0 entering the final 15 minutes of football.
Scott McTominay made his Man United debut off the bench five minutes from time, but a comeback was never likely as the home side closed out the final moments to secure a big three points.
The result has left Man United, who have lost for the first time in the league since October, four points behind fourth-placed Manchester City on the same number of matches, and Arsenal will now go above Mourinho's team if they win their game in hand.
Next up for Arsenal is a trip to Southampton on Wednesday night, while Man United will welcome Celta Vigo to Old Trafford on Thursday for the second leg of their Europa League semi-final, holding a 1-0 lead from the first leg in Spain.
