In Greek mythology, Crius, Kreios or Krios (Ancient Greek: Κρεῖος, Κριός) was one of the Titans in the list given in Hesiod's Theogony, a son of Uranus and Gaia. The least individualized among the Titans  he was overthrown in the Titanomachy. M. L. West has suggested how Hesiod filled out the complement of Titans from the core group—adding three figures from the archaic tradition of Delphi, Coeus, Phoibe, whose name Apollo assumed with the oracle, and Themis. Among possible further interpolations among the Titans was Crius, whose interest for Hesiod was as the father of Perses and grandfather of Hecate, for whom Hesiod was, according to West, an "enthusiastic evangelist".
Consorting with Eurybia, daughter of Earth (Gaia) and Sea (Pontus), he fathered Astraios and Pallas as well as Perses. The joining of Astraios with Eos, the Dawn, brought forth Eosphoros, the other Stars and the Winds.
Joined to fill out lists of Titans to form a total that made a match with the Twelve Olympians, Crius was inexorably involved in the ten-year-long war between the Olympian gods and Titans, the Titanomachy, though without any specific part to play. When the war was lost, Crius was banished along with the others to the lower level of Hades called Tartarus. From his chthonic position in the Underworld, no classical association with Aries, the "Ram" of the zodiac, is ordinarily made.
Aries is the first visible constellation in the sky at the spring season, marking the start of the new year in the ancient Greek calendar. This fact may have implied that Crius was the Titan god of constellations, measuring the duration of the year while his brother Hyperion measures the days and months.
- Etymology uncertain: traditionally considered a variation of κρῑός "ram"; the word κρεῖος was also extant in Ancient Greek but only in the sense of "type of mussel" .
- "About the other siblings of Kronos no close inquiry is called for," observes Friedrich Solmsen, in discussing "The Two Near Eastern Sources of Hesiod", Hermes 117.4 (1989:413–422) p. 419. "They prove useful for Hesiod to head his pedigrees of the gods", adding in a note "On Koios and Kreios we have to admit abysmal ignorance."
- M.L. West, "Hesiod's Titans," The Journal of Hellenic Studies 105 (1985), pp. 174–175.