With a freshly shaved line on the side of his head, soccer superstar Cristiano Ronaldo joined a training session with the Portugal national team ... gearing up for a 2018 World Cup run. 

Ronaldo looked Ronaldo-ish ... skilled, agile, rich ... and ran drills with teammates Pepe and Fabio Coentrao during the practice sesh in Lisbon.

By the way, the World Cup is gonna be here before you know it ... it's set to kick off on June 14 in Russia. 

Go USA.