Ronaldo, who was a free agent following his acrimonious split with Manchester United in November, joined Al Nassr last week on a 2-1/2 year deal estimated by media to be worth more than 200 million euros ($210.94 million).
He was greeted by a sea of yellow and blue at Al Nassr's home ground Mrsool Park, where thousands of fans turned up to witness his unveiling.
Ronaldo arrives in Saudi Arabia with a vast collection of club honours after a glittering spell at Spanish giants Real Madrid from 2009-18 where he won two LaLiga titles, two Spanish Cups, four Champions League titles and three Club World Cups.
He also claimed two Serie A titles and a Copa Italia trophy in three years at Juventus before rejoining United with whom he had bagged three Premier League crowns, the FA Cup, two League Cups, the Champions League and Club World Cup.
"I'm so proud to make this big decision in my life. In Europe, my work is done," Ronaldo told a news conference.
"I won everything, I played in the most important clubs in Europe and now it's a new challenge in Asia."
The 37-year-old batted away questions about criticism of his move to Saudi Arabia, saying, "I'm a unique player as well so for me it's normal."
Al Nassr coach Rudi Garcia said the signing of Ronaldo was a huge step for the Saudi Arabian league.
"Cristiano is one of the best players in the world and in the history of football. He is a legend, it is an honor for sure for me but also for Al Nassr to welcome Cristiano," Garcia told reporters.
Al Nassr president Mossali Al Muammar was also effusive in his praise of Ronaldo, calling him the "best player in football history."