Dolores Aveiro, 54, admitted that she is constantly bemused by tabloid speculation which surrounds her son's love life.
The Man United player has been romantically linked to an 18-year-old university student and a gym instructor in recent weeks.
However, responding to the rumours, Aveiro insisted: "My son has only introduced two girlfriends to me - Merche Romero and Nereida Gallardo.
"If I believed what other people say, he has been with more than 100 and he is a womaniser. But I know that it is not true. When he likes a girl and the relationship is serious, he presents her to his family."
Ronaldo dated Spanish model Gallardo for a brief period of time in 2008. Their partnership followed his earlier romance with Romero, a Portuguese TV star.
Aveiro made headlines in 2007 by claiming that Gemma Atkinson was telling lies about dating her son.