Kim Zolciak wants everyone to get their mind outta the gutter -- because her daughter did NOT Snapchat a plea for someone to bang her.

Kim tells us the Snap image of 20-year-old Brielle Biermann that's getting around is full-on FAKE NEWS ... or at least the caption is. She says Brielle really did post the photo, but her caption was "when u steal ur moms clothes."

She says some perv doctored up a new caption -- "still wanna f*** me in this Daddy?"