The Phantom Planet (ファントム・ガイア, Fantomu Gaia?) is an unnamed planet from which the Phantoms originate in Final Fantasy: The Spirits Within.
Similar in nature to Earth, the planet had its own spirit and supported a variety of life forms. One of its prominent species became embroiled in a cataclysmic war that destroyed the planet's environment and ultimately the planet itself.
A fragment of the planet was flung across space, becoming a meteor that crashlands on Earth and starts the Phantom invasion that devastates the living population.