The Portuguese, 35, drove himself into the Juventus Training Centre in a Jeep with tinted windows.
The five-time Ballon d’Or winner will undergo medical and physical tests before joining up with his teammates in training, according to media reports.
Juventus players returned to individual training on May 4, the day Ronaldo returned to Italy after spending lockdown in his native Portugal.
For the past two weeks, he has been in quarantine in his villa in Turin.
Ronaldo is the first Juventus foreign player, among those who left Italy during the lockdown, to return to the team’s Continassa training centre.
The Italian Football Federation (FIGC) announced on Monday that all its competitions, including Serie A, will remain suspended until June 14.
To see a pictures of the Juventus players and staff arriving for training, check out the photo gallery above.
Simply click on the arrows or swipe to view the next image.