Fernando Santos' side play two 2020 UEFA European Championship qualifiers in Lisbon in March. The defending champions take on Ukraine on March 22 and then play Serbia three days later.
Ronaldo asked to be left out of Portugal's games in September 2018, as he wanted time to adapt to his move from Real Madrid to Juventus, per Reuters.
The forward was also left out of the Portugal squad in October and November for games against Poland, Scotland and Italy, although no official reason was given for his absence.
Portugal fared well without their talisman. They are unbeaten in six games, winning three and qualifying for the finals of the UEFA Nations League.
However, they will be boosted by the return of Ronaldo, who is enjoying an impressive first season in Serie A.
Juventus are on course to retain their league title, with Ronaldo having contributed 19 goals and eight assists in 26 games.
He has also proven his worth in the UEFA Champions League. Ronaldo bagged a hat-trick in the last 16 to inspire Juve to a 3-2 aggregate win over Atletico Madrid, after losing the first leg 2-0.
The goals maintained his excellent strike rate in Europe's top competitions:
Ronaldo said after the win over Atletico that his Champions League record is why Juventus wanted to sign him, per Sky Sports.
"This was why Juventus brought me here, to help do things that they have never done before. This is the mentality you need to win in the Champions League. I just do my work and I'm very happy tonight, it was a magical night. Atletico are always difficult to face, but we are also strong and we proved it."
Ronaldo has already achieved success at international level with Portugal after helping them win Euro 2016. He's also his country's all-time record goalscorer and has over 150 caps for the national team.