The Portugal forward saw his stint at Old Trafford brought to an early conclusion by mutual agreement last month after an inflammatory interview with Piers Morgan where he revealed his unhappiness with United and its manager Erik ten Hag.
Ronaldo has been in action for Portugal at the World Cup in Qatar, scoring in its opening game of the tournament to become the first man to net at five different World Cups.
The 37 year-old wished to leave United ahead of the 2022-2023 season, and confirmed in his interview with Morgan that he had turned down a lucrative offer from a Saudi Arabian club.
However, Marca on Tuesday (AEDT) reported that Riyadh-based side Al Nassr is close to signing the five-time Ballon d'Or winner.
A move to the gulf state would mark the end of Ronaldo's illustrious career in Europe, having starred for United, Juventus and Real Madrid - indeed, he is Los Blancos' record goalscorer.
No player has scored more in the Champions League than Ronaldo, who is also the highest goalscorer in international football, with 188 to his name.
At Al Nassr, he is expected to net close to €200million per season, with additional economic incentives, a sum that would make him the highest-paid athlete in the world.
Al Nassr's squad also includes Cameroon's World Cup star Vincent Aboubakar and former Napoli goalkeeper David Ospina.
Ronaldo originally returned to United ahead of the 2021-2022 campaign, but has mostly been frozen out under new boss Erik ten Hag this season, prompting an explosive interview that contributed to his departure.