In Greek mythology, Theia (/ˈθiːə/; Ancient Greek: Θεία, romanized: Theía, also rendered Thea or Thia), also called Euryphaessa "wide-shining", is the Titaness of sight and by extension the goddess who endowed gold, silver and gems with their brilliance and intrinsic value. Her brother/consort is Hyperion, a Titan and god of the sun, and together they are the parents of Helios (the Sun), Selene (the Moon), and Eos (the Dawn). She may be the same with Aethra, the consort of Hyperion and mother of his children in some accounts.

The name Theia alone means simply "goddess" or "divine"; Theia Euryphaessa (Θεία Εὐρυφάεσσα) brings overtones of extent (εὐρύς, eurys, "wide", root: εὐρυ-/εὐρε-) and brightness (φάος, phaos, "light", root: φαεσ-). Once paired in later myths with her Titan brother Hyperion as her husband, "mild-eyed Euryphaessa, the far-shining one" of the Homeric Hymn to Helios, was said to be the mother of Helios (the Sun), Selene (the Moon), and Eos (the Dawn).