The former Barcelona and Real Madrid forward paid around 30 million euros, according to Spanish media reports.
Valladolid were promoted this season and Ronaldo said the aim was to keep the team in the Spanish top flight.
"We want Real Valladolid to consolidate in the top flight and keep building hopes from there," said Ronaldo.
"It will not stop there because we want to grow to where our hopes allow us to."
Suarez will continue as club president.
"The arrival of Ronaldo puts Valladolid on the map and will allow the club to take a leap forward in quality. I welcome him to his home," said Suarez.
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