On which planet does Metroid Prime take place?

Metroid Prime takes place on the planet Tallon IV. Samus travels there after responding to a distress signal from the Space Pirate frigate Orpheon, beginning an investigation that uncovers the planet's catastrophic history.

Tallon IV was once home to a Chozo civilization. About five decades before the game, a meteor struck the planet and brought a mutagenic substance that the Space Pirates named Phazon. The Chozo built the Artifact Temple to contain the impact crater and prevent the corruption from spreading across the world.

Samus explores several distinct regions of Tallon IV, including the forested Tallon Overworld, the volcanic Magmoor Caverns, the frozen Phendrana Drifts, and the contaminated Phazon Mines. These areas connect the game's environmental exploration with its central mystery about Phazon and the creature known as Metroid Prime.

Tallon IV is often confused with Aether, the setting of Metroid Prime 2: Echoes, or SR388, the Metroids' original homeworld. Zebes is instead associated with the original Metroid and Super Metroid.