No, Cristiano Ronaldo is Catholic (Christianity). You can see this using his first name: Christiano. The root of this name is Christian. If you are referring to the Brazilian Ronaldo, the same is true. He is Catholic. He is a footballer. read more
Cristiano Ronaldo sometimes used to give Salam (Greetings for Muslims) to Mesut Ozil. He is also very Close to his Team mate, Karim Benzena, who is also a Practicing Muslim. Although he is very sympathetic towards Muslims, he has not converted to Islam and is a Christian. read more