A court in Milan Wednesday announced that the American actor and the Portuguese footballer are among potential 78 defence witnesses. Prosecutors also presented the court with a list of 138 people it may want to call.
Clooney and Ronaldo reportedly attended parties hosted by Berlusconi. The actor also owns a house in Milan.
Berlusconi resigned earlier this month amid a financial crisis.Critics say the sex trial and other trials for corruption linked to his media empire distracted the billionaire's ability to guide the country, and are a national embarrassment.
Berlusconi's social life has been in the public eye since it emerged that starlets and prostitutes were guests at his villas where he held sex parties.