The Portuguese has hit the ground running since joining in the summer, scoring six goals in his opening eight games.
Ronaldo is just a few months away from his 37th birthday but continues to perform at a high level every week.
But where does he currently rank among the world's best strikers?
FourFourTwo have named the 10 best number nines in the world right now.
View their selections below...
10. Lautaro Martinez (Inter Milan)
9. Edinson Cavani (Manchester United)
8. Ciro Immobile (Lazio)
7. Karim Benzema (Real Madrid)
6. Romelu Lukaku (Chelsea)
5. Cristiano Ronaldo (Manchester United)
4. Harry Kane (Tottenham Hotspur)
3. Kylian Mbappe (Paris Saint-Germain)
2. Erling Haaland (Borussia Dortmund)
1. Robert Lewandowski (Bayern Munich)
FourFourTwo think that Ronaldo is now only the 5th best striker in the world.
One of the players who has been ranked higher than him is Kane.
There's no doubting that Kane is a phenomenal striker, but he has struggled at the start of the 2021/22 season.
After his future at Spurs came into question this summer, Kane has begun the campaign with just one goal from his opening seven Premier League games.
But it's Lewandowski who tops the list - and rightly so.
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The Polish striker scored his 54th goal of 2021 against Hoffenheim on Saturday - which is a quite ridiculous tally.
He's not only the world's best striker but he has a very good chance of winning the Ballon d'Or in a month's time.
Luis Suarez and Zlatan Ibrahimovic are among the big names that didn't make the top 10 altogether.