The Horus Heresy is an ongoing series of science fantasy set in the fictional Warhammer 40,000 setting of tabletop miniatures wargame company Games Workshop. Penned by several authors, the series takes place during the Horus Heresy, a fictional galaxy-spanning civil war occurring 10,000 years prior to the far future of Warhammer 40,000. The war is described as a major contributing factor to the game's dystopian environment.
The books are published in several media by the Black Library, a Games Workshop division, with the first title released in April 2006; as of October 2017 the work consist of 48 published volumes, with more in the pipeline.
The series has developed into a distinct and successful product line for the Black Library; titles have often appeared in bestseller lists, and overall the work has received critical approval despite reservations.