What race created the Metroids?

The Chozo created the Metroids. In Metroid lore, the technologically advanced birdlike species engineered them as a biological weapon against the X parasites, a dangerous shapeshifting organism native to SR388.

The Metroids initially served an important defensive purpose: they preyed on the X and helped stop the parasite from spreading. Their success created a new problem, however. Metroids could evolve into larger and more dangerous forms, and eventually became a threat to the Chozo themselves. This cycle of creation, containment, and attempted weaponization drives much of the series’ history.

Metroid Dread adds more detail by identifying the Thoha, a peaceful and scientifically inclined Chozo tribe, as the group that genetically engineered the Metroids. The Mawkin tribe later viewed the creatures as potential weapons, creating a major conflict within Chozo society.

The Space Pirates and Galactic Federation did not create the species. Both groups later tried to capture, study, clone, or weaponize Metroids, which is why they are often associated with their history. The Luminoth are a separate species from Aether and had no role in creating them.