'CR7' has gone on to make the Champions League his own, scoring a record 120 goals in 154 appearances and picking up a winners' medal on a record-equalling five occasions.
However, exactly 15 years ago on Monday, he made his first apperance on the biggest stage in club football as a fresh-faced 19 year-old winger.
Facing Stuttgart, Ronaldo lined up alongside the likes of Gary Neville, Paul Scholes, Roy Keane and Ryan Giggs, all of whom had won the competition with the 'Red Devils' juut four years before.
He had appeared in the qualifying stages during his time at Sporting Lisbon, but this was his first time in the competition's group-stage.
Despite not scoring in the 90 minutes, in a collision between Ronaldo and goalkeeper Timo Hildebrand saw United awarded a penalty, that Ruud Van Nistlerooy dispatched to score the team's only goal of the night.
The German outfit had already scored two goals through Imre Szabics and Kevin Kuranyi, meaning that Ronaldo lost his first European encounter 2-1.
A decacde and a half later, he has become the undisputed goal-scoring king of the competition, and will hope to add a sixth Champions League to his trophy cabinet with Juventus.