Jennifer Aniston, Courteney Cox, Katy Perry Celebrate Jennifer Meyer's 40th Birthday

Jennifer Meyer's 40th birthday party turned into THE non-Coachella celeb event of the weekend ... with Jennifer Aniston, Courteney Cox, Katy Perry ... AND Orlando Bloom all showing up.

The huge bash went down at Peppermint in WeHo, where Justin Theroux was hanging with the wife and her "Friends" pal. Jessica Alba, Nicole Richie and a bunch of other celebs were inside.

As for Katy and Orlando ... no word if they saw each other inside, but there was at least a chance.

Jewelry designer Meyer and Tobey Maguire split up last year. Kinda obvious now who got the bulk of their famous pals in the breakup.

At least he's got Leo DiCaprio.