Cristiano Ronaldo admits ... his 5-year-old son does NOT know the identity of his birth mother -- and Ronaldo says he feels no obligation to tell him for at least another 5 or 6 years.
The soccer superstar appeared on "The Jonathan Ross Show" in the U.K. and was asked about his mysterious baby mama ... who he's kept secret since Cristiano Jr. was born.
FYI -- Ronaldo's kid was born in the U.S. in 2010. He was given full custody.
"For me it is not a problem," Ronaldo said ... "In the world, many kids don’t have mum, don’t have dads or dads die or mums die."
"Cristiano has a dad, an unbelievable dad, a grandmother. I have the support of my family, great of course."
"When Cristiano is going to grow up, I am always going to say the truth to him because he deserves, because he is my son but I am not going to say because people want me to say."
As for when he'll reveal the mommy mystery to his son, Ronaldo says ... "I’m going to say the time when I feel that is the right time. I don’t know 10, 11, 12? I don’t know let’s see."
BTW, Ronaldo says he's dating right now -- courting a "few" women at the same time. When asked if they knew about each other, Ronaldo said, "I need to figure out who is better. Some know, yes."