The Austrian-born actor and former professional bodybuilder says that the Real Madrid star possesses a "fantastic physique" which has helped him to reach the top of his game
Ronaldo has been in excellent form so far this season, scoring 12 goals in 10 games for Los Blancos in all competitions, though his side are third in La Liga and five points behind both Barcelona and Atletico Madrid.
Speaking to COPE ahead of the 2013 Arnold Classic, a professional bodybuilding contest hosted in Madrid, the Austrian-born actor enthused about Ronaldo's condition.
"He has a fantastic physique," said the 'Predator' star.
"He has some great abs - he looks spectacular. He looks to be in great shape, so it is clear he's a great footballer."
The 66-year-old Hollywood star, who rose to fame with leading roles in films such as 'Conan the Barbarian' and 'The Terminator', was also asked if Ronaldo had what it took to compete against him in the prestigious bodybuilding competition Mr Olympia - a title that Schwarzenegger has won seven times.
"I don't think he'd be interested in competing in a Mr Olympia," said the former govenor of California, laughing off the question.
"He is interested in being the best player in the world. I was interested in winning the Mr Olympia title. They are two different sports but there is no doubt he is in great shape."