Penumbra: Requiem, developed by Frictional Games, is the third game in the Penumbra series. It is a survival horror puzzle game available on the Windows platform. The game picks up right where the previous game ends, with the protagonist, Phillip, trying to escape from a research complex. The game revolves around the notes of another scientist who was also trapped in the complex.

The game features a highly sophisticated physics engine, which allows players to interact with in-game items by moving the mouse. Unlike the previous games, the player cannot put items in their inventory but can still move them around the world. The game features no weapons, and the only way to avoid getting killed is to run away and hide. Players have to find keys to activate a portal that leads them off the level. These keys are usually placed in hard-to-reach spots and require a lot of thinking to acquire.

Penumbra: Requiem has two endings, which are chosen by the players themselves and are not affected by the players' actions throughout the game.