Tom Brady, DiCaprio, Sweeney, Bloom Form Party Central at Venice Hotel

Tom Brady, Leo DiCaprio, Orlando Bloom and Sydney Sweeney are in the thick of party central at the Jeff Bezos and Lauren Sanchez wedding in Venice ... and it sounds like Tom's making a move.

We've learned the most hopping place in the Floating City is The Gritti Palace ... a landmark waterfront hotel where a collection of Jeff and Lauren's most famous friends are staying -- and it's the place to be for wedding guests looking to party.

Sources who are there tell us Tom, Leo, Orlando, Sydney, Jerry Seinfeld, Oprah, Charissa Thompson and the Kardashians are all staying at the Gritti ... and Sydney is the "center of attention" for single guys, including TB12.

We're told the gang's been hanging at the hotel bar, partying and dancing ... and Tom is taking center stage as the life of the party -- even spending some time chatting up Sydney, who one source described as "f***ing beautiful" in person.

While the Gritti is crawling with hot ladies, we're told this has become more about the guys bonding with each other than trying to hook up with women.

Case in point ... our sources say Tom, Leo, Orlando and Scooter Braun ventured over to the swanky Hotel Cipriani on Friday afternoon ... hanging out and drinking by the pool. Plus, we're told the Kardashians aren't exactly throwing themselves out there, and are mostly keeping it all in the family.

Friends are staying at the Cirpiani, family is shacking up at the Aman ... leaving The Gritti Palace as the party zone.

Speaking of parties ... Thursday night was the Gatsby-esque cocktail party, and tonight, after the wedding ceremony, there's another secret party ... no one knows where that is.

Our sources say security at the wedding is "unbelievable" as Jeff and Lauren try to keep things super private.