Ronaldo was born in Bento Ribeiro, a poor neighborhood in Rio de Janeiro, Brazil. Like many of his friends, he began to play football in the streets of his neighborhood. Ronaldo's actual date of birth is September 18, 1976, however, his father did not register his birth certificate until September 22 1976 so some discrepancy has existed as to his actual birth date.

In April 1999, Ronaldo married Milene Domingues. The marriage lasted four years and ended in divorce. The couple had a son, Ronald (born 2000). In 2005, Ronaldo got engaged to Brazilian model and MTV VJ Daniela Cicarelli, who became pregnant but suffered a miscarriage; their relationship lasted 3 months after their engagement. He ended his relationship with Brazilian supermodel Raica Oliveira in December 2006. Writer Andrew Downie asserted a correlation between Ronaldo's personal life and performance on the pitch, noting that his most prolific periods of goalscoring have coincided with the times when he was happily married.

In 2005, Ronaldo became co-owner of A1 Team Brazil, alongside Brazilian motorsports legend Emerson Fittipaldi. The team participates in the A1 Grand Prix series, with Nelson Piquet, Jr., Tony Kanaan and João Paulo Oliveira as drivers for the debut season.

International career
AC Milan
Personal life
Football career