Confronting Evil: Assessing the Worst of the Worst is a non-fiction hardcover book by Bill O'Reilly and Josh Hammer, published by St. Martin's Press (Macmillan) on September 9, 2025. An instant #1 New York Times bestseller, this 304-page volume is the latest entry in Bill O'Reilly's Confronting Series, examining the nature of evil through the lives and actions of history's most destructive figures.

The book chronicles the deeds of history's most notorious individuals and groups, including Genghis Khan, the Roman Emperor Caligula, Henry VIII, 19th-century slave traders, 20th-century robber barons, Stalin, Hitler, Mao, the Ayatollah Khomeini, Vladimir Putin, and the Mexican drug cartels — figures collectively responsible for the death and suffering of hundreds of millions of people. By recounting what they did and why they did it, O'Reilly and Hammer illuminate the timeless struggle between good and evil.

Drawing on the Judeo-Christian tradition and John Stuart Mill's warning that "bad men need nothing more to compass their ends, than that good men should look on and do nothing," the authors challenge readers to confront the reality of evil and the moral imperative of action over indifference. The book is available in hardcover, eBook, audiobook, large print, and audio CD editions.