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*Dyḗus (lit. 'daylight'), also *Dyḗus ph₂tḗr (lit. 'father daylight'), is the reconstructed name of the daylight-sky god in Proto-Indo-European mythology. *Dyēus was conceived as a divine personification of the bright sky of the day and the seat of the gods, the *deywṓs. Associated with the vast diurnal sky and with the fertile rains, *Dyēus was often paired with *Dʰéǵʰōm, the Earth Mother, in a relationship of union and contrast.
While its existence is not directly attested by archaeological or written materials, *Dyēus is considered by scholars the most securely reconstructed deity of the Indo-European pantheon, as identical formulas referring to him can be found among the subsequent Indo-European languages and myths of the Vedic Indo-Aryans, Latins, Greeks, Phrygians, Messapians, Thracians, Illyrians, Albanians and Hittites.