George Clooney -- The Final Hoorah ... Before Tying the Knot

George Clooney said arrivederci to freedom with the boys Friday night in Italy ... the day before he ties the knot with Amal Alamuddin.

Clooney and Amal starred at a rehearsal dinner with family and friends in Venice ... and it looks like they went on separate journeys afterward with their respective genders.

Clooney hit up a restaurant with all the other dudes -- it's unclear where Amal went.

Most of George's famous friends are also in Venice for the wedding ... including Bono, Bill Murray, Matt Damon and Ellen Barkin.

Now it's only a matter of time.