What a night at Bramall Lane!
Lys Mousset's first goal on home soil on his first league start was enough to beat Arsenal in front of the Sky cameras.
The French striker applied the finishing touch from close-range in the first-half as United produced arguably their best performance of the season to beat Unai Emery's side.
For the clash against the Gunners, boss Wilder made two changes from the starting XI that drew with Watford before the international break, as Mousset was handed a first league start alongside the fit-again McGoldrick in attack.
United were typically quickly out of the blocks and forced a couple of corners inside the opening three minutes. At the other end, the visitors then had a flurry of corners in quick succession, the last of which left Stevens needing treatment.
On 15 minutes, following another Blades corner, Fleck was booked for a foul on Aubameyang. Six minutes later, United had a let off, as a counter-attack resulted in Xhaka played in Kolasinac down the left, but Pepe failed to make a clean connection with the goal at his mercy.
But on the half hour the roof at the Lane literally came off, as United deservedly hit the front from Norwood's corner. O'Connell got up highest at the back post, which gave MOUSSET the opportunity to apply the finishing touch from inside the six yard box.
The atmosphere inside S2 was electrifying, although when Saka went down with Egan's challenge approaching there was a sharp intake of breath, only for referee Dean to book the Arsenal man for simulation. O'Connell was then carded for trying to halt the progress of Pepe, as the Gunners broke at pace.
Two minutes of added time were signalled, and Henderson was brought into action to deny Xhaka from over 30 yards out, before Sokratis headed the resulting corner high and wide, as United went into half-time with the advantage.
Arsenal made a change at the break, with Ceballos replacing Willock. Ten minutes into the second period, goalscorer Mousett received a warm applause as Sharp was introduced in his place.
The Blades crafted the first real chance shortly afterwards, with Sharp and Fleck combining to free Baldock, but he fired wide from a promising position. At the other end, Ceballos should have done better, from Saka's cross.
On the hour, more patient play from the Blades ended with Fleck firing an effort at goal, it had Leno, but unfortunately for United it was into the side-netting. McGoldrick and Kolasniac were booked, before Fleck's stinging effort from distance almost got the better of Leno. In response, Lacazette won a free-kick, but Henderson was equal to Pepe's effort, before United's number one was scrambling across his goal when the same player shot wide moments later.
With the clock ticking down, McGoldrick was replaced by Luke Freeman, before McBurnie was introduced in place of Norwood and within a minute the Scottish international won a free-kick which saw Sokratis booked.
Five minutes of added time were shown by the fourth official and United continued to defend resolutely, as the crowd drove the Blades over the finishing line to register a famous and deserved victory.
Blades: Henderson, Baldock, Stevens, Fleck, O'Connell, Basham, Lundstram, Egan, Norwood (McBurnie 85) McGoldrick (L. Freeman 78), Mousset (Sharp 55).
Unused: Robinson, Jagielka, Moore, Bešić.
Arsenal: Leno, Chambers, Sokratis, David Luiz, Kolasinac, Xhaka (Lacazette 69), Guendouzi, Willock (Ceballos 45), Pepe (Martinelli 78), Saka, Aubameyang.
Unused: Martinez, Holding, Tierney, Torreira.
As it happened...
Ball takes a huge ricochet after Fleck hammers the ball at an Arsenal and spins behind for a corner.
Blades take it short, it is drilled into the near post and cleared.
Good start by United who are on the front foot, as Arsenal survive another corner. 0-0.
Pepe slides a cross into the six-yard area, and United clear.
Arsenal then have a trio of corners which are all cleared by the Blades. 0-0.
Break in play as Stevens is down injured...
Stevens is okay, we're back underway. 0-0.
Clever throw by Stevens earns United a corner.
Norwood swings it in but a ruck of Arsenal bodies clear at the near post. 0-0.
Late challenge by Fleck on Aubameyang results in a yellow card.
Great work by McGoldrick winning the ball high up pitch. He finds Fleck who drills a low cross into the mix, aimed at Mousset who was lurking, but Arsenal make a crucial interception. 0-0.
Stevens then smashes a low shot into the area, and it hits Mousset but bounces to safety - could have gone anywhere. 0-0.
Great chance for Arsenal as a low cross from Kolasinac just needs a firm contact from Pepe, but he somehow fails to make a meaningful connection and United clear. 0-0.
Good pressure again from United as Stevens drills a low cross into the near post, corner...
GOAL FOR UNITED!!!!!!!!!!!!!!!!!!!
Norwood corner into the back post, O'Connell heads it into the six-yard area and Mousset is there to convert!!
Baldock goes down under a challenge in the area, no penalty says the ref. 1-0.
Drama at the other end as Saka then goes down in the area and the referee books him for simulation.
A member of the Arsenal staff is then cautioned for antics on the sidelines.
Booking for Jack O'Connell as he tries to halt an Arsenal counter-attack
Xhaka with a 30-yard strike which looks destined for the top corner, only for Henderson to push behind with a wonderful save.
Arsenal head wide from the corner.
Two minutes added time.
Blades 1 - 0 Arsenal
Mousset's goal has United in the lead at the break.
Teams back out here for the second half
Arsenal change at the start of the second half.
Dani Ceballos for Willock.
Pepe wins Arsenal a corner, it is zipped into the near post where Lundstram heads clear. 1-0.
Arsenal on the front foot at the start of the second half.
United have Egan to thank for a great interception as the visitors cross from the right. 1-0.
Deep cross from Fleck picks out Mousset in the area, but he brings the ball under control with his hand and Arsenal get a free-kick. 1-0.
Change for United as Mousset is replaced by Sharp.
Brilliant play by Sharp who chests the ball into the path of Fleck. He immediately plays it into the onrushing Baldock who fires wide. 1-0.
Cross by Saka finds Ceballos who scuffs his effort harmlessly into the arms of Henderson. 1-0.
Terrific build up play by Lundstram as he finds Fleck who drills an effort from the angle into the side netting. 1-0.
Blades break through McGoldrick who goes down and is booked for simulation.
There's also a card Kolasinac for Arsenal.
Stinging effort from Fleck from 25 yards is spilled by Leno, but he just gets to the loose ball ahead of McGoldrick.
Arsenal change as Lacazette replaces Xhaka.
Two important headed clearances from Basham and Baldock as Arsenal threaten again. 1-0.
Attendance: 30,775 (2,856)
Foul by McGoldrick, Arsenal free-kick 25 yards from goal.
Pepe sends it over the wall but it is a comfortable height for Henderson who saves.
Pepe is a lot closer with his next effort which flies just wide of the far post with Henderson at full stretch.
Henderson booked for time wasting on the restart.
Baldock with a charging run down the right, the ball inside the area finds Sharp with his back to goal, he lays off for Norwood who crashes an effort wide. 1-0.
Sub for Arsenal, Pepe off, Martinelli on.
United change as McGoldrick is replaced by Luke Freeman.
Guendouzi works his way to the by-line, his cut-back is blocked for a corner which is headed clear. 1-0.
Oli McBurnie replaces Norwood.
Booking for Sokratis after a late challenge.
Chamers drills a ball across the area, it takes a deflection and sails wide. The resulting corner is cleared. 1-0.
Five minutes added time.
Blades 1 - 0 Arsenal
Mousset's first-half goal wins it for United!