The couple were joined by 60 of their closest friends, who had travelled from all over the world to celebrate their wedding in the grounds of Villa Baroncino, overlooking the shores of Lake Trasimeno.
Katrina wore a Jenny Packham dress and Luke a tailored suit from Dress2Kill.
After the ceremony, the newlyweds danced the night away, finally leaving the party as their friends went skinny-dipping in the moonlight.
The couple later marked their union with Italian engravings inside their wedding bands. They read, "The Princess found her Frog" and "The Frog found his Princess".