Pariah is a first-person shooter video game developed by Digital Extremes. It was released in May 2005 for Microsoft Windows and Xbox. It uses a modified version of the Unreal Engine 2 and the Havok physics engine. A PlayStation 2 version was also in development but cancelled.

Pariah features standard first-person shooter gameplay, largely influenced by the Unreal franchise, particularly Unreal 2 (whose game engine Pariah is based on). The single-player and multiplayer modes include drivable vehicles that can be utilized in combat scenarios. One of the standout features is the incorporation of collectible weapon energy cores, which are used to upgrade the player's weapons, granting them additional features and increased power. Each weapon in the game can be upgraded a maximum of three times.

Pariah notably omits to explain key background information about the plot and the in-game universe to the player, thus causing much of the story to progress without any context or background for the player to identify with. Even at the end of the game, many key plot points remain largely unexplained, leaving it up to the player to conjecture about what really happened.

The game takes place 30 years after mankind fought a devastating war against an enemy known as "The Shroud". Exactly who or what the Shroud are is never actually explained. At the end of the game, they are shown to be hairless humans with corpse-white skin and highly advanced technology, although whether they are aliens, terrorists, mutants, or something else is never clearly revealed. Supposedly, the Shroud were vanquished 30 years ago, but their reappearance toward the end of the game indicates that this is not true.

In the wake of the war, a large portion of the Earth is now an uncivilized wasteland known as "the Zone", inhabited by Scavengers, the violent descendants of prisoners and convicts who were released by the Shroud during the war. Human civilization is now controlled by a government known as the Alliance. According to the game manual, the Alliance mostly lives in off-world colonies on other planets, but this is never shown or mentioned in the game.

Jack Mason is a medic for the Alliance, tasked with transporting a cryogenically frozen woman named Karina from the maximum security prison "the Anvil" to Alliance headquarters. While flying over "the Zone", Mason's ship is shot down by a surface-to-air missile, crash-landing on Earth. Mason is accidentally infected with the mysterious transgenic virus that Karina is carrying, and she escapes in the chaos that follows as Scavengers arrive at the crash site attempting to capture her. The pilot, Stubbs, is killed in the fracas, but Mason manages to outfight them and the Mercenaries. Mason suspects there is an unusual nature behind the apparent Scavenger attack, as they were not known to possess surface-to-air missiles.

Although Karina is highly distrustful of Mason, her former captor, the two of them team up to evade the Mercenaries. Mason observes that Karina possesses bizarre powers granted to her by the virus; when experiencing strong emotions, she involuntarily produces an explosive effect that creates mass destruction while leaving her unharmed. Eventually, Mason and Karina succeed in radioing the Alliance for help, only to learn that Colonel Stockton, the Warden of "the Anvil", has ordered the Alliance to nuke the area and kill everything that moves, supposedly to contain the infection and prevent the spread of the virus. Karina is soon captured by Alliance Security, and Mason finds himself fighting against the very organization he works for.

As Mason infiltrates "the Anvil" to retake Karina from Stockton, he finds the Mercenaries have also launched a massive assault against the Anvil for revenge. It becomes evident that Stockton masterminded the attack on Mason's transport and that he has paid off the Mercenaries to capture Karina for him. However, it turns out that Stockton has double crossed the Mercenaries by allowing The Alliance to capture Karina for himself and refusing to pay them. Stockton is obsessed with battling the Shroud and wants to use the virus Karina carries as a weapon against them. The Alliance had deemed Stockton's research dangerous, which led him to continue his project in secret.