The Callisto Protocol is set on Callisto, one of Jupiter’s moons. The game follows Jacob Lee after his spacecraft crashes on the Jovian moon, where he is imprisoned in the heavily fortified Black Iron Prison.
Callisto is the second-largest of Jupiter’s four Galilean moons and is known for its heavily cratered surface. Scientists have also considered whether it may contain a subsurface ocean, a possibility that helped make it an attractive setting for the game’s isolated, potentially habitable future.
The PUBG connection needs context. Striking Distance Studios was originally formed within PUBG Corporation to create a narrative game expanding the PUBG universe, and The Callisto Protocol was initially presented as part of that timeline. In 2022, director Glen Schofield said the project had become its own story and world, although small PUBG references remained.
Callisto is often confused with Europa, another Galilean moon that is especially famous for evidence of a subsurface ocean. The game’s location, however, is Callisto, not Europa, Ganymede, or Io.