Russian Billionaire's Son Drops $100,000 on Champagne for Zac Efron & Pals

Zac Efron went to Chicago ... and all he got was a $100,000 bottle of champagne from the son of a Russian billionaire!!!

Efron was at the Board Room nightclub Tuesday night -- for an event organized by Elite Entertainment -- along with Heather Graham and other people from a movie they're working on together.

Sources at the club tell us ... the Russian saw the actors and wanted to send them a gift, so he fired over a 15 litre bottle of Armand de Brignac Nebuchadnezzar Champagne, also known as "Ace of Spades."

The Russian also bought some stuff for his OWN table, including 2 magnum bottles of Grey Goose, 2 magnum bottles of Dom Perignon, 4 bottles of Cristal and 3 magnum bottles of Laurent-Perrier Brut Rosé.

The total bill -- $112,550 ... PLUS -- dude dropped a $22,510 TIP for his server, Jasmine -- 20%.

Not bad for a Tuesday night.