"Bad Girls Club" star Stephanie Rivera loves big butts (she cannot lie) ... telling TMZ she plans to get a big new ass to go along with her big new boobs.
Rivera says she's going under the knife Sunday in Miami for a Brazilian Butt Lift -- a process in which a doctor sucks fat out of her abdomen, back and love handles ... and then injects it into her derriere to give her a sexier, hourglass shape.
Stephanie -- who recently got her B-size breasts augmented to full C's -- says she couldn't get the shape she wanted by working out ... so she's getting the BBL to take care of her excess flab and her sorry-ass ass at the same time.
Her doctor -- Michael Salzhauer -- tells TMZ, "Curvy is the new sexy," ... and says JLo, Kim K and Nikki Minaj have the butts women ask for most.
Fun fact: Salzhauer says more than 10,000 U.S. women got BBLs last year ... and about 5% of his patients are men.