CHAOS: Charles Manson, the CIA, and the Secret History of the Sixties is a 2019 nonfiction book written by Tom O'Neill with Dan Piepenbring. The book presents O'Neill's research into the background and motives for the Tate–LaBianca murders committed by the Manson Family in 1969. O'Neill questions the Helter Skelter scenario argued by lead prosecutor Vincent Bugliosi in the trials and in his book Helter Skelter (1974). The book's title is a reference to the covert CIA program Operation CHAOS.