Mbappe has often been linked with a big-money move to Madrid but has two years remaining on his contract.
Former Madrid star Ronaldo is a majority shareholder of LaLiga side Valladolid and can only dream of being in a position to sign the World Cup winner, who had scored 18 goals in 20 league appearances before the season was cut short in France.
Speaking at a media event sponsored by Santander Bank, Ronaldo said: "I would sign Mbappe [if Valladolid had Madrid's money], he is the one who most reminds me of me and my playing times."
Ronaldo also spoke of his admiration for Erling Haaland, but is not convinced Madrid would need the Borussia Dortmund striker while they have Karim Benzema.
"Haaland is a great player, he is still young and has had a pretty good year with many goals, we will see how he ends it," he said.
"Surely big teams are going to be watching, but Real Madrid have good players, like Benzema who scores goals every Sunday."