The Portuguese striker was on 799 career goals going into the game at Old Trafford.
And he managed to become the first top-flight player to hit 800 goals in the 52nd minute.
Marcus Rashford picked out Ronaldo in the box and the 36-year-old made no mistake from close range to make it 2-1 to United.
Martin Odegaard restored parity moments later but Ronaldo would score the winner for his side in the 70th minute.
United were given a penalty when Fred was felled by Odegaard inside the box and Ronaldo would make no mistake as he blasted the ball past Aaron Ramsdale.
It was another historic day for Ronaldo who once again proved why he's the best goalscorer of all-time on Thursday evening.
But, for some odd reason, Ronaldo still has his fair share of haters.
Ronaldo's critics often make the argument that most of his goals are either tap-ins and penalties.
And that was exactly what Twitter user @Bibococo1 did after Ronaldo scored his 801st goal in football.
Cristiano Ronaldo SINKS Arsenal as Man United win 3-2! Full reaction on The Football Terrace...
Replying to a tweet from Gary Lineker, the football fan branded Ronaldo: "Tapinaldo and a Penaldo".
It's no secret that Lineker thinks that Lionel Messi is the greatest player of all-time.
But he couldn't resist hitting back at the fan for 'disrespecting' the Portuguese legend.
He wrote: "That’s as ridiculous as it is disrespectful. @Cristiano is indisputably one of the greatest players in the history of the game. An absolute phenomenon."
Well said, Lineker.
It's absolutely ludicrous that Ronaldo still has haters when he's scored over 800 goals in professional football.
The numbers he's put up over the past two decades have been absolutely insane and, at the age of 36, he continues to perform at the highest of levels.
It'll be a very long time until another player comes around like Ronaldo, that's for sure.