The two international stars were called by the now former-prime minister's defense lawyers and approved by a judge on Wednesday.
Berlusconi hopes that the celebrity witnesses will testify that they never saw the politician pay for sex with an underage prostitute during one his infamous bunga bunga parties.
It may sound like the plot of a Hollywood movie, but Berlusconi stands trial for paying for sex with a Moroccan-born exotic dancer named Karima El Mahroug who goes by the stage name Ruby. While prostitution isn't a crime in Italy -- even for a politician in office -- El Mahroug was only 17 years old at the time, making the alleged act illegal.
Both Berlusconi and Ruby deny that they ever had relations. Nonetheless, the dancer will be one of 136 witnesses called on by the prosecution. (Berlusconi's defense team has slated 78 witnesses.)
Berlusconi has also been charged with abuse of office for allegedly using his position to get El Mahroug released from police custody.
According to The Associated Press, Berlusconi claimed that he got the teenager off of a theft charge because he thought at the time that she was Egyptian President Hosni Mubarak's niece.
The defense hopes that Ronaldo will discredit whatever damaging testimony El Mahroug might give. The dancer has said on record that she met Ronaldo in Milan, but the soccer player denies the claim. The same is true for Clooney, whom Ruby said she met at a dinner with Berlusconi.
In October, Clooney detailed the one and only evening he spent with the Italian prime minister and media mogul. He allegedly visited Berlusconi's house in Rome, not Milan as El Mahroug claimed, where he tried to get Berlusconi to send humanitarian aid and helicopters to the Darfur region of Sudan.
“I've had one evening with Berlusconi and it was one of the more astonishing evenings of my life, Clooney said in an interview with Time Magazine last month.
“I went to speak about Darfur. I'd done my homework. He took me to see his bedroom and the bed that [Vladimir] Putin gave him. It became a very different evening than anyone thought. I was like ‘I have to go’ and he was saying ‘Where are you going, there's going to be a party,’ and I was like 'No, I gotta go, I really do.’”
I wasn't at his 'bunga bunga' party, Clooney added.
Also among the witnesses will be Clooney's ex-girlfriend, Italian model Elisabetta Canalis.