In Greek mythology, Theia (also written Thea or Thia), also called Euryphaessa ("wide-shining"), was a Titan. With her brother and husband Hyperion, she was the mother of Helios (the Sun), Selene (the Moon) and Eos (the Dawn). The name Theia alone, means simply "goddess," Theia Euryphaessa with overtones of brightness.

Pindar praises Theia in his 5th Isthmian ode:

"Mother of the Sun, Theia of many names, for your sake men honor gold as more powerful than anything else; and through the value you bestow on them, o queen, ships contending on the sea and yoked teams of horses in swift-whirling contests become marvels".

She seems here a goddess of glittering in particular and of glory in general, but Pindar's allusion to her as "Theia of many names" is telling, since it suggests assimilation not only to similar mother-of-the-sun goddess like Phoebe and Leto, but perhaps also to more universalizing mother-figures like Rhea and Cybele.

Theia's mythological role as the mother of the Moon goddess Selene is referenced in the application of the name to a hypothetical planet which, according to one theory, collided with the Earth, resulting in the Moon's creation. See Theia (planet).