Ronaldo, who has scored in every Euros since his first appearance in 2004, has netted 14 goals in the finals. He also scored 10 times in European qualifying matches last year.
Ronaldo now plays for Saudi Pro League side Al-Nassr where he has scored 42 goals and provided 13 assists in all competitions.
"Cristiano? It's better to talk about the data. He's a player who's scored 42 goals in 41 games for his club," Martinez said.
"That shows his continuity and physical ability to always be fit, as well as the quality he has in front of goal, which we really like and need."
However, Ronaldo will not be the oldest member of the squad with Martinez also calling up Porto defender Pepe who turned 41 this year.
Pepe was an integral part of Porto's team this year, making 38 appearances as they reached the Champions League last 16 and finished third in the league behind Sporting and Benfica. They are also in the Cup final.
"Pepe's role in the dressing room is important, the way he represents the national team shirt. I think that during the training camp, football is a constant struggle," Martinez added.
"And it was interesting to see Pepe play two games in March and keep a clean sheet for the 90 minutes he played. His communication, his positioning mean that, when he's fit, he's a very important player."
PORTUGAL'S SQUAD FOR EUROS
Goalkeepers: Diogo Costa (Porto), Jose Sa (Wolves), Rui Patricio (Roma)
Defenders: Antonio Silva (Benfica), Danilo Pereira (Paris SG), Diogo Dalot (Man United), Goncalo Inacio (Sporting), Joao Cancelo (Barcelona), Nelson Semedo (Wolves), Nuno Mendes (Paris SG), Pepe (Porto), Ruben Dias (Man City)
Midfielders: Bruno Fernandes (Man United), Joao Neves (Benfica), Joao Palhinha (Fulham), Otavio Monteiro (Al Nassr), Ruben Neves (Al-Hilal), Vitinha (Paris SG)
Forwards: Bernardo Silva (Man City), Cristiano Ronaldo (Al Nassr), Diogo Jota (Liverpool), Francisco Conceicao (Porto), Goncalo Ramos (Paris SG), Joao Felix (Barcelona), Pedro Neto (Wolves), Rafael Leao (AC Milan).Â
