You may not be immediately aware but this week marked an anniversary of a fairly significant moment in football's modern era.
Messi and Ronaldo first faced each other 12 years ago when Barcelona and Manchester United played out a goalless draw in the first leg of the Champions League semifinals -- the former aged 20, the latter 23.
Ronaldo's United won through on that occasion (despite the Portugal star missing a penalty in the first leg) and went on to become European champions. At the end of the following season, he sealed his world-record £80 million move to Real Madrid and thus joined his future rival in La Liga.
The pair have since tangled a total of 36 times, with some truly memorable encounters. Here are six of the best.
1. The Champions League final (Manchester United 0-2 Barcelona, May 27, 2009)
The 2009 final in Rome was hyped as a gladiatorial clash between the two best players in the world, and this time Messi came out on top.
Barca successfully kept United at arm's length in Rome to win 2-0 and secure their first ever league, cup and European Cup treble.
2. "La Manita" (Barcelona 5-0 Real Madrid, Nov. 29, 2010)
The game that was seen as something of a proving ground for both Messi and Ronaldo (who were both Ballon d'Or winners by this point) ultimately veered off script as the Camp Nou witnessed a historic humiliation of Real and their coach, Jose Mourinho.
Messi did not score, but he set up two goals and had another of his own disallowed as he played a pivotal role in Barca dishing out a five-goal mauling of their foes, who had started the game top of La Liga and unbeaten in seven matches.
The hefty scoreline was duly immortalised by Gerard Pique's five-fingered "Manita" ("Little Hand") salute toward the Real supporters.
3. Ronaldo's revenge (Real Madrid 1-0 Barcelona, April 20, 2011)
Twelve years ago today, Messi and Ronaldo faced each other for the first time.— ESPN FC (@ESPNFC) April 23, 2020
The beginning of an incredible rivalry 🤝 pic.twitter.com/yiQy4ZTA7J
Having largely been on the losing side in the opening knockings, Ronaldo finally triumphed over Barca as a Real player at the fifth time of asking.
The Madrid forward was the only scorer as his trademark towering 103rd-minute header saw Los Blancos snatch the Copa del Rey from beneath Barca's noses.
However, that final at the Mestalla came in the middle of an intense run of four Clasicos in three weeks, which culminated in Barca reaching the Champions League final at the expense of their bitter rivals.
4. Ronaldo strikes again (Barcelona 1-2 Real Madrid, April 21, 2012)
Ronaldo again prevailed when the old adversaries met at the Camp Nou toward the tail end of the 2011-12 league campaign.
Barca surrendered their hopes of defending the La Liga title as a winner from Ronaldo put Los Blancos seven points clear at the top of the table with four matches left to play.
Ronaldo's goal also saw Real break the Spanish league scoring record with goal number 109 of the season and they romped to the title soon thereafter.
5. "Shush!" (Barcelona 1-3 Real Madrid, February 26, 2013)
Long-awaited payback for Ronaldo came in the latter stages of the 2012-13 Copa del Rey when the Real man turned in a star performance to send Barcelona packing.
After the first leg had ended 1-1 at the Bernabeu, the Portuguese forward scored twice and almost single-handedly wrapped up a 3-1 win at the Camp Nou in the return to seal Real's place in the final.
By the end of the game, Mourinho was brazenly shushing the home fans with his finger pressed against his lips and Ronaldo left the ground having scored in each of his last six appearances on Barca's hallowed turf.
6. The shirt celebration (Real Madrid 2-3 Barcelona, April 23, 2017)
Messi once again seized the last laugh after a 92nd-minute winner from the Argentine talisman nicked a very late victory at the Bernabeu and kept Barca's title aspirations alive.
Having already scored in the first half, Messi kept his cool to slot home an injury-time winner amid a hostile atmosphere and then celebrate by pointedly reminding the Real supporters of his name.
In the entire nine-year period that Messi and Ronaldo were together in Spain, there was never a goalless Clasico.
Box office, guaranteed.