Other stars who have arrived include Ellen Barkin - who threw Amal a hen party several weeks ago - Miguel Ferrar, Vogue editor Anna Wintour, Cindy Crawford, and her husband Rande Gerber, while U2 frontman Bono is also expected to attend.
Cindy's husband Rande is expected to act as George's best man.
CLICK ON PICTURES FOR GALLERYrecently married in an intimate ceremony in France, are reported to have booked a suite at the Belmond Hotel Cipriani, where George and Amal are expected to host a rehearsal dinner on Friday.
George's former co-star Sandra Bullock is also rumoured to be a guest.
Amal and George, 53, are expected to marry on Saturday at a waterside location – possibly at the 7 star Aman Canal Grand Venice Hotel which has magnificent views - and it is thought that the Grand Canal will be closed off to allow the pair to proceed down Venice's famous waterways after the ceremony as a flotilla of gondolas follow them.
It has also been reported that between 50-150 guests will be there to witness George and Amal seal their one-year courtship. The ceremony will reportedly be conducted by George's friend, and the former mayor of Rome, Walter Veltroni, while Oscar winner George will be wearing an Armani suit.
Showing no signs of last-minute nerves, the striking bride-to-be looked happy and relaxed as she made her way through Milan airport on Wednesday with her mother Barria by her side.
Amal managed to keep her arrival low-key – despite the excitement surrounding her marriage to one of Hollywood's biggest stars. She smiled as she wheeled along her suitcase, carrying a large box and a Stella McCartney garment bag slung over her shoulder.