Portugal will meet Switzerland in the semi-finals on June 5 in Porto, with the winner set to play England or the Netherlands for the title on June 9 at the same venue.
"Cristiano is our leader and it's always better to have the best player in the world with us," said Lille defender Jose Fonte.
Ronaldo sat out Juventus' final Serie A game of the season at the weekend, a 2-0 defeat away to Sampdoria.
He finished his debut campaign in Italy with 21 league goals in 31 appearances.
He was recalled by Fernando Santos in March for Portugal's opening Euro 2020 qualifiers, having not played for his country since the 2018 World Cup.