The Kardashians: Quit Using Us for Facelifts!

Kim Kardashian and her family just dropped the hammer on a plastic surgeon who's been cashing in with something called the "Kardashian Facelift."

According to docs obtained by TMZ ... the Kardashians sicced their attorney on Dr. Gary Eldridge, demanding he quit using their name to promote his product, or else.

TMZ broke story ... the Australian doc had filed docs to trademark the fibrin protein treatment in the U.S. He even claimed it was named after his family dog, and NOT Kris Jenner's krew.

But the letter to Dr. Eldridge informs him the family already holds countless trademarks on its name for beauty, cosmetics and all sorts of advertising, upon which he is infringing.

In plain English: Beat it, doc ... we're working this corner!