Clooney, 53, revealed the news when he and Alamuddin attended a charity gala in Florence, reported Ace Showbiz.
"I met my lovely bride-to-be in Italy (and) will be marrying (her) in a couple of weeks, in Venice," he said during an appearance at a charity gala Celebrity Fight Night in Florence.
Alamuddin was also present at the event which was held in support of the Andrea Bocelli Foundation and the Muhammad Ali Parkinson Center. She wore a black strapless gown by Dolce & Gabanna.
A few days ago, Alamuddin was spotted at Alexander McQueen's headquarters in Clerkenwell, East London. She was accompanied by her mother Baria for a trip to Michael John hair salon before heading to the fashion house for a 90-minute appointment.