Clooney, 53, and Alamuddin, 36, solemnised their relationship in Venice, Italy, where they had first met, reported People magazine.
"It feels pretty damn great. We're looking forward to everything," he said.
On choosing Venice as the venue for the ceremony, the Oscar-winner said, "(Venice is) the most romantic city in the world... We met in Italy. We have a home there. We knew that was where we wanted to get married."