Reese Witherspoon to Cara Delevingne -- How the **** Do You Pronounce Your Name?

You're not the only one who can't pronounce Cara Delevingne's name -- Reese Witherspoon can't either, neither can Kate Upton or Zooey Deschanel ... and they all proved it during a hilarious drunk elevator ride earlier this week.

Cara posted the footage to her Instagram account after an evening at the Met Gala Monday night -- showing the hottest group of women ever to assemble in an elevator, and they're all joking about how to pronounce Cara's (Cah-ra's?) name.

The video is hilarious -- but the award goes to Reese for her attempt ... "Delevig-ny."

Cara has since deleted the footage -- but here they are again in all their glory.