Jeff Bezos is keeping it classic on his wedding day ... because he's rocking a tuxedo.

Check out these photos of Jeff before his star-studded wedding to Lauren Sanchez Friday in Venice, Italy ... dude's looking dapper.

Bezos is smiling and waving ... pairing some circular rimmed sunglasses with his black-and-white tux.

We've already shown you Lauren's pre-wedding look ... the bride-to-be was snapped today with two gigantic diamond rings on her fingers ... one on each hand.

Lauren was blowing a kiss at photos and showing off the huge rocks ... one is a pillow-cut and the other is an oval the size of an egg.

Jeff and Lauren's impending nuptials are bringing out some of Hollywood's biggest names ... and everyone will be dressed to the nines for the actual ceremony.