Al-Nassr had to come from a goal behind against fellow Saudi club Al-Hilal to lift the trophy, eventually winning 2-1 after a tense period of extra time.
In an eventful final, Al-Hilal opened the scoring through Michael early in the second half before Al-Nassr was reduced to 10 men with 20 minutes remaining following Abdulelah Al-Amri’s red card.
Ronaldo’s first goal drew the sides level after 74 minutes, but things got even more complicated for Al-Nassr after Nawaf Boushal was shown a red card to leave his side with just nine men.
Despite the numerical disadvantage, Ronaldo headed home a rebound to score his second and the winning goal nine minutes into extra time.
The Arab Club Champions Cup features the biggest clubs from Saudi Arabia, Qatar, the United Arab Emirates, Morocco, Tunisia, Algeria and Iraq, and Ronaldo finished as the tournament’s top scorer with six goals in six games.
However, the Portuguese forward is now an injury doubt for Al-Nassr’s Saudi Pro League (SPL) opener against Al-Ettifaq on Monday after being stretchered off with an injury with five minutes remaning.
Ronaldo signed a two-and-a-half year contract reported to be worth more than 200 million euros ($220.16 million) with Al Nassr in December after leaving Manchester United.
The 38-year-old said in June that any new signings for Saudi clubs would be “very welcome” to join him in the league.
Since then, Karim Benzema, N’Golo Kante, Kalidou Koulibaly, Edouard Mendy and Roberto Firmino have been among the star names to move to the SPL, while Sadio Mané and Marcelo Brozović have joined Ronaldo at Al-Nassr.