A Planet Fitness gymgoer was arrested after allegedly walking around totally naked in the women's locker room ... claiming they identified as a woman, something the gym didn't buy.
Christopher Miller -- identified as male by online booking records -- was arrested in Gastonia, NC Thursday for indecent exposure after gymgoers claim he walked into the women's locker room at a local Planet Fitness.
A shocked woman reportedly called the police when she saw Miller, telling the 9-1-1 operator a fully naked man wouldn't leave the room ... adding he identified himself as a woman when asked to do so.