The Portugal captain has signed a two-year contract with the Saudi Arabian outfit after his contract with Manchester United was terminated back in November.
Reports earlier on Tuesday suggested Ronaldo could make a return to England and sign for Newcastle United on loan next season, should Eddie Howe's side qualify for the UEFA Champions League.
Ronaldo is a five-time Ballon D'or winner and has also won league titles in England, Spain and Italy.
The 37-year-old has won the UEFA Champions League five times and captained Portugal to European championship glory in 2016.
Ronaldo claims he received several offers from all over the world but settled on Al Nassr to help the development of the game in Saudi Arabia.
"I'm so proud to make this big decision in my life and in football," Ronaldo said at his unveiling on Tuesday.
"In Europe, my work is done. I won everything and played for the most important clubs in Europe.
"This is a great opportunity for me, not only in football but to change the mentality of the new generation in Saudi Arabia.
"I had many opportunities in Europe, in Brazil, in the United States and even in Portugal, but I gave my word to this club, for the opportunity to develop football in this amazing country."
"Many people speak and give their opinions, but really they know nothing about football," Ronaldo added as he responded to critics of his choice of destination.
"If you give the example of the World Cup, the only team who beat the champions [Argentina] was Saudi Arabia, don't forget that.
"For me, it's not the end of my career. I wanted to change and I don't worry about what people say. I took my decision and I have responsibility for it.
"I'm happy to be here and I know the league is really competitive, I saw many games. I'm ready to play tomorrow [against Al Ta'ee] if the coach thinks it's good!
"I beat all records in Europe, so I want to beat all records here. This contract is unique, because I'm a unique player. So for me, this is normal.
"I'm coming here to win, to play, to enjoy, to be part of the success of the country and the culture of the country. What I want is to enjoy, to smile and to play football."
