As reported by Brazilian newspaper O Globo, the 41-year-old is in advanced negotiations to buy Valladolid for €30m (£26.3m).
The two-time World Cup winner has already gained experience working at boardroom level in a football club. Back in 2014, he was the part-owner of North American Soccer League side Fort Lauderdale Strikers before selling his 20 per cent share in the club last year.
In January, Ronaldo spoke of his ambition to own a second-tier side in either Spain or England.
He told La Folha de Sao Paulo. "It would be a great honour to preside over the Brazil Football Federation, but before I want to have experience managing a great club.
"I am thinking about buying a team in the second division in Spain or England. I want to do something innovative. I think I'm ready for that challenge."
According to Marca, the club's majority shareholder and president Carlos Suarez denies any offer has been tabled, but €30m would be enough to strike a deal.
Valladolid currently sit sixth in the Segunda Division standings. The Castile and Leon side host Osasuna on Saturday, the final day of the regular season, as they look to cement a play-off spot.
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