With new interim manager Ralf Rangnick watching from the stands, the German was given a glimpse of both the talent he will have to work with and problems he has to solve at Old Trafford.
Arsenal went ahead in bizarre circumstances as Emile Smith Rowe’s shot trickled in with United goalkeeper David De Gea down injured before Bruno Fernandes levelled.
Ronaldo’s 800th career goal was quickly cancelled out by Martin Odegaard.
But the five-time Ballon d’Or winner had the final say when he crashed home a penalty 20 minutes from time.
A vital victory for United cuts the gap between the sides to two points in the battle for a place in next season’s Champions League.
Three points also rounds off a fine stint for Michael Carrick in caretaker charge since Ole Gunnar Solskjaer was sacked after progress to the Champions League last 16 and a creditable 1-1 draw at Premier League leaders Chelsea.
The United fans paid homage to Solskjaer with a banner in the first match at Old Trafford since he was dismissed.
However, once the action got underway, nothing seemed to have changed from the final days of the Norwegian’s reign as United started in a similar fashion to humiliating home defeats to Liverpool and Manchester City.
Pierre-Emerick Aubameyang and Ben White had chances for the visitors inside the first two minutes.
When Arsenal did go in front on 13 minutes it was in strange fashion.
Smith Rowe’s shot bounced into an unguarded net with De Gea down injured having been stood on by his own player Fred.
Referee Martin Atkinson blew the whistle to stop play, but only after the ball had crossed the line and therefore the goal had to stand.
Arsenal players rebuffed United’s request to stand aside and allow them to equalise in a gesture of fair play.
But they did so of their own accord a minute before half-time when Jadon Sancho and Fred combined to tee up Fernandes to slot home his first goal since September.
In stark contrast to a cagey first 45 minutes, the second period raged from end to end.
De Gea made amends for his part in the opening goal with a flying save to deny Gabriel before Aaron Ramsdale produced an even better stop at the other end to divert Ronaldo’s drive to safety.
Ronaldo was dropped to the bench by Carrick at Stamford Bridge on Sunday amid suggestions that may become a more common occurrence under Rangnick’s high-energy style.
Accommodating the 36-year-old has been one of the causes of United’s decline defensively this season.
But Ronaldo has kept his end of the bargain with 12 goals in 17 games since returning for a second spell with the Red Devils.
He coolly slotted home Marcus Rashford’s cross, but United’s lead lasted just two minutes as Arsenal responded with almost a carbon copy equa
This time Gabriel Martinelli was the provider for Odegaard to steer into the far corner.
However, on the night he reached another remarkable personal milestone, the stage was set for Ronaldo to breathe new life into United’s season when Fred was chopped down inside the box by Odegaard.
Fernandes blasted over when he retained penalty duties against Aston Villa earlier in the season.
This time he stood aside for his international teammate, who smashed the ball high past Ramsdale for his 130th United goal across two spells.
Ronaldo also scored 450 goals for Real Madrid, 101 at Juventus, five for Sporting Lisbon and is the record goalscorer in international football with 115
Wow
Ronaldo
Great team
Wonderful
Really good
Great
Dg
Good
Sure good
Ok
Gosh
I don’t know
Lovely
Fantastic
Just
Yap
Just 1
Yes 1
Just 2
Hahaha
Just 3
Ok
Just 4
Ftu
Just 5
J
Just 6
7 oo
Just 7
Just 8
6one
Just 9
Just 0
Ok 2
Just 10
12
Mark
Just 11
Gdj
Just 12
2jt
Just 13
Dm
Just 14
Just 15
Just 16
Uyt
Adgaj
Halo
Ronaldo
Puw
Amazing
T t
interesting
Ronald
O
M
Good
Tw
A1
A2
A3
A4
Great team
A5
A6
A7
A8
A9
A10
Ao
A11
Adcs
Nk
Jhhhj
Yeah
B1
B2
B3
B4
B5
B6
B7
B8
B9
B10
B0
B11
What
2go
Great!
Fire🔥🔥
Good
On fire
Men
Cool
Fine too see
B14
B15
B16
B17
B18
B19
B20
B21
B22
B23
B24
B24s
B25
B26
B27
B28
B29
B30
35
Nice
Good mar
Wow that
Ok 1
Ok 2
Ok 2a
Ok 3
Ok 4
Ok 5
Ok 6
Wonderful
Ok 7
Ok 8
Ok 9
Ok 10
67
Rufai
Keep
Karen
Kareem
Open
Close
Jump
John
Joe
Jot
Please
Police
Poe
Poet
Post
Go
Come
Love
Left
Ok
Fatastic
nice one
alright
Grab
nice
How
Seriously
Awesome
1
Great
Ronaldo
Wow
Great
How many
Yap
Nice game
Wow..
Good One
Best of carrick
Nice post
Carrick is good
Excellent
Both win
Nice
Cool
Win
That’s great
C Ronaldo is a legend too in football
Hmm
lies
Good
They are progressing
Great
Ok
Ok