Ann Rule (born October 22, 1935, in Lowell, Michigan) is an American true crime writer.
Rule got her start writing for the magazine True Detective under the presumably male nom de plume Andy Stack. When she started writing for the magazine in 1969, the editor suggested she write under a male name in order to be taken seriously as a crime writer despite having a short stint as a police officer herself (with the Seattle Police Department). After proving her ability in several magazines, including Master Detective, Inside Detective, Front Page Detective, and Office Detective she was invited to start writing under her own name, but decided to keep the pen name at that time in the interest of protection for herself and her family from her subjects.
She came to prominence with her first book, The Stranger Beside Me, about serial killer Ted Bundy. At the time she started researching the book, the murders were still unsolved. In the course of time, it became clear that the killer was Bundy, her friend and previous colleague on the suicide hotline at the King County Crisis Clinic. She has also met and interviewed a number of other serial killers in the course of researching her books.