|Full name||Ronaldo Guiaro|
|Date of birth||18 February 1974|
|Place of birth||Piracicaba, Brazil|
|Height||1.86 m (6 ft 1 in)|
|Playing position||Centre back|
|XV de Piracicaba (coach)|
|2017||XV de Piracicaba|
|* Senior club appearances and goals counted for the domestic league only|
Born in Piracicaba, São Paulo, Ronaldo started playing with Guarani Futebol Clube, moving to Clube Atlético Mineiro shortly after. In 1996, aged 22, he joined S.L. Benfica in Portugal, backing up Jorge Bermúdez and Hélder Cristóvão in his first season but being first-choice afterwards, as the Lisbon and Primeira Liga club failed to win any silverware.
After five seasons with Benfica, Ronaldo signed for Beşiktaş J.K. in Turkey, also being an undisputed starter for the majority of his spell. In the 2002–03 campaign he only missed one Süper Lig match, as the Istanbul-based team was crowned national champions after an eight-year wait.
Aged 31, Ronaldo returned to his country but, two years later, moved abroad again, going on to be a defensive mainstay with Aris Thessaloniki F.C. in the Superleague Greece for several seasons whilst helping it qualify three times to the UEFA Cup/UEFA Europa League.
- Atlético Mineiro
- Campeonato Mineiro: 1995
- Taça de Portugal: Runner-up 1996–97
- Campeonato Paulista: 2006, 2007
- Greek Football Cup: Runner-up 2007–08, 2009–10