Orion Publishing Group Ltd. is a British publishing company owned by parent company Hachette Livre, based in London. It was founded in 1991. Orion was responsible for publishing Aliens, Predator and Aliens vs. Predator novels in the United Kingdom between 1992 and 1997, releasing these novels under the science-fiction imprint Millennium.
All of the novels published by Orion were adaptations of Dark Horse Comics comic book series, with just one exception — Aliens vs. Predator: Hunter's Planet was an original story. Following the publication of Predator: Cold War in 1997, the rights to publish Aliens/Predator/Aliens vs. Predator novels moved to Dark Horse through their subsidiary DH Press, and new books shifted away from comic book adaptations and began to focus on original stories.
Orion was only responsible for Aliens/Predator/Aliens vs. Predator novels in the United Kingdom; in the United States, these novels were instead published by Bantam Books. Orion never actually published the final three novels produced by Bantam (Aliens: Berserker, Predator: Big Game and Aliens vs. Predator: War), meaning these books are only available in the UK as imports.
- Aliens: Earth Hive by Steve Perry
- Aliens: Nightmare Asylum by Steve Perry
- Aliens: The Female War by Steve Perry and Stephani Perry
- Aliens: Genocide by David Bischoff
- Aliens: Alien Harvest by Robert Sheckley
- Aliens: Rogue by Sandy Schofield
- Aliens: Labyrinth by S. D. Perry
- Aliens: Music of the Spears by Yvonne Navarro