'True Blood' Star Ryan Kwanten -- REJECTED from Oscar Party

11:40 AM PT -- Sources connected to the party tell TMZ ... Kwanten was invited to the party as a guest of George Clooney and his GF Stacy Keibler ... and SHOULD have been on the list.

We're told party organizers are trying to find out how Kwanten's name was left off the list ... but it's clear the actor wasn't trying to crash the party uninvited.

TV stars get no respect on Oscar night ... just ask "True Blood" star Ryan Kwanten ... who was embarrassingly REJECTED at the door of a huge Academy Awards party ... and TMZ caught the whole thing on tape.

Kwanten -- sporting a fancy bow tie -- arrived to Craig's in Hollywood with a handler last night ... when they came face-to-face with the security team guarding the front door.

Kwanten and his buddy insisted they were personally invited by Craig himself ... but the bouncer wasn't buyin' it.

Kwanten's handler even whipped out his cell phone and got someone important on the phone to vouch for him ... but when he gave the phone to the bouncer, the security guy STILL wouldn't let him in.

Eventually, Kwanten and his buddy took the note and walked away ... but not before the handler asked the bouncer which company he worked for ... insinuating that heads would ROLL over the rejection.

Don't worry Ryan ... at least you're still pretty.