Ronaldo “is asymptomatic” and “will not play against Sweden” in Wednesday’s Nations League match, the federation said on its website.
The 35-year-old forward for Juventus, who has been voted the world’s top player five times, played in Portugal’s goalless Nations League draw against France on Sunday.
Ronaldo has scored 101 goals for Portugal and will be a huge absence for his team against Sweden as they aim to hold on to top spot in their group.
The test result which also means Ronaldo is a doubt for Juventus’ Champions League group match with Barcelona on October 28, which was set to pit Ronaldo against his old rival Lionel Messi.
Ronaldo, who has featured for Manchester United and Real Madrid, is the highest-profile footballer to test positive for Covid-19, which has killed over a million people since the beginning of the pandemic earlier this year.
Brazil forward Neymar, his Paris Saint-Germain teammate Kylian Mbappe and AC Milan striker Zlatan Ibrahimovic have also tested positive for the virus in recent weeks.