Ronaldo was strongly linked with a move to the Saudi Pro League side after his second spell at Manchester United ended in acrimonious fashion in late November.
After falling down the pecking order at United, Ronaldo – who only scored one Premier League goal this season – told Piers Morgan he had no respect for head coach Erik ten Hag in a controversial interview.
That comment, as well as Ronaldo's declaration that United had "betrayed" him, led the Red Devils to terminate his contact shortly after the start of the World Cup in Qatar.
Al Nassr emerged as frontrunner for his signature and waited patiently before before the 37-year-old's transfer was officially confirmed on Saturday (AEDT).
Ronaldo has signed a two-and-a-half-year deal with reports suggesting he will earn more than £60million ($A106m) per season.
In his interview with Morgan, aired shortly before the World Cup, Ronaldo claimed to have turned down a move to Saudi Arabia during the off-season transfer window.
On his arrival at Al Nassr, however, Ronaldo said he was inspired by his new club's vision.
"I'm thrilled for a new experience in a different league and a different country, the vision that Al Nassr has is very inspiring," he said.
"I'm very excited to join my team-mates, and to help the team to achieve more success."
Al Nassr labelled Ronaldo's transfer as "history in the making".
History in the making. This is a signing that will not only inspire our club to achieve even greater success but inspire our league, our nation and future generations, boys and girls to be the best version of themselves. Welcome @Cristiano to your new home @AlNassrFC pic.twitter.com/oan7nu8NWC— AlNassr FC (@AlNassrFC_EN) December 30, 2022
"This is a signing that will not only inspire our club to achieve even greater success but inspire our league, our nation and future generations, boys and girls to be the best version of themselves. Welcome @Cristiano to your new home @AlNassrFC."
Ronaldo's move is seen as effectively bringing down the curtain on one of the greatest careers in the history of elite European Football.
He has lifted the Champions League trophy on five occasions – four times with Real Madrid and once with United, while his tally of 140 goals is the highest recorded in Europe's premier club competition.
Ronaldo is also Madrid's all-time top scorer with 450 goals, while he became the highest-scoring player in the history of men's international football last year – he now has 118 senior goals for Portugal.
However, he has fallen short of those incredible standards in recent months, with a group-stage penalty against Ghana representing his only goal at the 2022 World Cup in Qatar, though that did make him the first man to net at five different editions of FIFA's flagship tournament.
Having been relegated to the role of substitute for Portugal's last two games, Ronaldo maintained his unwanted record of never scoring in a knockout fixture at the World Cup before watching his great rival Lionel Messi lead Argentina to a third title.
Al Nassr is coached by former Lyon boss Rudi Garcia and has Cameroon forward Vincent Aboubakar and ex-Arsenal goalkeeper David Ospina on its books.
The Riyadh-based side has won Saudi Arabia's top flight on nine occasions – a tally only bettered by Al Hilal, which has 18 titles to its name.
Al Nassr is second in the Saudi Pro League after 10 games, just two points adrift of leader Al Shabab.
Ronaldo could potentially be available to make his Al Nassr debut on Friday 6 January (AEDT), at home against Al Ta'ee.