Clint Eastwood's Daughter Francesca -- I'm Getting an Annulment From Jonah Hill's Bro

Francesca Eastwood's marriage to Jonah Hill's brother will end faster than you can say Britney Spears and Jason Alexander ... because she's getting the week-long marriage annulled ... TMZ has learned.

Sources close to the regretful couple tell us ... the notion of getting hitched was fueled by alcohol -- and lots of it. Francesca and Jordan Feldstein ended up in a cheesy Vegas wedding chapel and took their vows amidst faux greatness -- an Elvis impersonator.

Francesca had immediate regrets. We shot her the day after the nuptials and she wasn't wearing a wedding ring.

We shot Clint Eastwood a few weeks ago asking for marriage advice and he told our photog to not rush into anything.

Guess Francesca should have listened.