The Minds of Billy Milligan is a 1981 non-fiction novel by Hugo Award-winning author Daniel Keyes.

It tells the story of Billy Milligan, the first person in U.S. history acquitted of a major crime by pleading dissociative identity disorder.

[1] A sequel, The Milligan Wars,[2] was published in Japan in 1994.

The book inspired the 2023 Apple TV+ miniseries The Crowded Room, starring Tom Holland and Amanda Seyfried.