The Champions League group stage begins on Tuesday night and this season, the huge matchups kick-off in week one.
Napoli v Liverpool and Borussia Dortmund v Barcelona are tonight's exciting fixtures, while Atletico Madrid v Juventus and Paris Saint-Germain v Real Madrid stand out on Wednesday.
It's not just Europe's biggest clubs in competition each week, as the best players on the continent will be going head-to-head too.
Both players thrive on the biggest stage and they're two of the Champions League's greatest ever players. But who is currently leading the way in the European Cup?
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The stats confirm it's Ronaldo - and by quite a distance too. Check out the breakdown below.
Messi vs Ronaldo:
Games: 135 vs 162
Goals: 112 vs 126
Assists: 30 vs 38
Average goals per game: 0.8 vs 0.7
Braces: 25 vs 27
Hat-tricks: 6 vs 7
Penalty goals: 12 vs 16
Headers: 4 vs 24
Free-kicks: 5 vs 12
Last 16 goals: 26 vs 23
Quarter-final goals: 12 vs 25
Semi-final goals: 6 vs 13
Final goals: 2 vs 4
As you can see, Ronaldo leads Messi in pretty much every stat, except for goals in the last 16 and average goals per game.
So, as it stands, the Juventus forward is currently the best player in the Champions League.
But that can all change. Messi isn't far behind in any category and could catch his great rival if Barcelona have a better season.
On matchday one, the Blaugrana visit Borussia Dortmund in Group F, while Juve travel to Spain to face Atletico Madrid, kicking off Group D.
Both clubs are amongst the favourites to go all the way to the Champions League final - and that's mostly down to the fact they have Messi and Ronaldo.
But on an individual level, it will be very interesting to see if the Portuguese can keep his crown as the European GOAT this season, or if his Argentine rival will wrestle it back.News Now - Sport News