Gaia or Gaea was the goddess or personification of Earth in ancient Greek religion, one of the Greek primordial deities. Gaia was the mother of all: the heavenly gods, the Titans and the Giants were born from her union with Uranus (the sky), while the sea-gods were born from her union with Pontus (the sea). The Greek word "γαῖα" (transliterated as gaia or gaea) is a collateral form of "γῆ" meaning Earth. Her equivalent in the Roman pantheon was named Gaea (Terra in more ancient documents). This is alluded to in Final Fantasy IX with the existence of Gaia's twin world.
The mythological name Gaia was revived in 1979 by James Lovelock, whose Gaia hypothesis proposes that living organisms and inorganic material are part of a dynamic system that shapes the Earth's biosphere, and maintains the Earth as a fit environment for life. In some Gaia theory approaches the Earth itself is viewed as an organism with self-regulatory functions. This theory is especially alluded to in the Final Fantasy: The Spirits Within take on Gaia as the planet's soul.