Kim Kardashian's famous ass just got jacked by Liziane Gutierrez ... who paid top dollar to get it.

The Brazilian model dropped $25,000 to go under the knife last month in her home country and pump up her booty. We're told she received injections of hyaluronic acid, which doesn't show up on X-rays ... critical to the booty community, apparently.

Liziane came out of the hour-long procedure with 39" hips. She's hoping her new digits -- 36-26-39 -- can win Brazil's famed Miss BumBum contest later this year.

Let the games begin!