Malice Aforethought (1931) is a murder mystery novel written by Anthony Berkeley Cox, using the pen name Francis Iles. It is an early and prominent example of the "inverted detective story", invented by R. Austin Freeman some years earlier. The murderer's identity is revealed in the first line of the novel, which gives the reader insight into the workings of his mind as his plans progress. It also contains elements of black comedy, and of serious treatment of underlying tensions in a superficially respectable community. It is loosely based on the real-life case of Herbert Armstrong, with elements of Doctor Crippen.

Malice aforethought was the "premeditation" or "predetermination" (with malice) that was required as an element of some crimes in some jurisdictions, and a unique element for first-degree or aggravated murder in a few. Insofar as the term is still in use, it has a technical meaning that has changed substantially over time.