The superstars met in the Champions League group stages last season.
Ronaldo's Juventus won 3-0 at the Camp Nou with the Portuguese scoring twice against Messi and co.
Their rivalry will go down as one of the greatest in history with both players doing all they can to be crowned the best player in the world over the past years
Between them, 12 of the last 13 Ballons d'Or have been won by the pair, with Luka Modric pipping them both in 2018.
The duo are friendly off the pitch, often seen chatting with their families at awards ceremonies, but when the whistle blows and both are on the field only winning matters.
Now, the world will be watching again with United and PSG set to clash in the last-16 of this season's elite European tournament.
But what is their head-to-head record? talkSPORT.com have taken a look at the statistics.
So, when it comes to their head-to-head record, it's Messi who is the victor.
The Argentine has six more wins in games between the two players, while he has one more goal than Ronaldo, and an astonishing 12 assists, showing his all-round impact in games.
Back in 2018, their final El Clasico match against each other ended in a 2-2 draw in LaLiga between Real Madrid and Barcelona.
Ronaldo only managed 45 minutes of football but still claimed a goal, as did Messi, with the pair ending their historic Spanish rivalry with the spoils shared.