Considering being Jeffrey Dahmer for Halloween? Simone Biles says you better think twice about the costume ... telling people it's NOT okay to wear the 'fit.
"im just gon go head and say it," the Olympic gold medalist announced on Twitter on Tuesday, "put the jeffrey dahmer costumes back in the closet. we ain't having it!!!!!!"
The killer-themed getup has been a popular one this month ... in wake of the new Netflix show which shined a light on the murderer's life.