Aliens versus Predator is a science fiction first-person computer game developed by Rebellion and published by Sierra. It was officially released for PC and Mac in 1999, followed by an unofficial port to Linux in 2001, following Rebellion's public release of the game's source code. A sequel to ]Aliens vs Predator, Aliens vs. Predator 2, was developed by Monolith Productions, and released by Sierra in 2001.