Congratulations Miss Vietnam USA -- you've just won $10,000 (which you're not getting) and a new car (which you have to finance yourself).

According to a lawsuit filed earlier this week in Orange County, Yen Le -- who was crowned Miss Vietnam USA in November 2007 -- is suing the pageant organizers because she alleges she was supposed to receive $10,000 and a new Mercedes for winning.

Now get this -- not only does she claim she never got the $10K, but she says the pageant made her lease the car in her own name ... and then they defaulted on the payments.

She's suing for over $50K in damages, plus interest, attorneys' fees and court costs.