The sky often has important religious significance. Many religions, both polytheistic and monotheistic, have deities associated with the sky.
The daylit sky deities are typically distinct from the night-time sky (or "heaven of the stars") deities. Stith Thompson's Motif-Index of Folk-Literature reflects this by separating the category of "Sky-god" (A210) from that of "Star-god" (A250).
Daytime-gods and Nighttime-gods may also be deities of an "upper world" (or "celestial world"), opposed to a "netherworld" (or "chthonic realm") ruled by other gods (for example, Sky-gods Zeus and Hera rule the celestial realm in ancient Greece, while the chthonic realm is ruled by Hades and Persephone), or of an upper world and netherworld respectively.
Any masculine sky god is often also king of the gods, taking the position of patriarch within a pantheon. Such king gods are collectively categorised as "Sky father" deities, with a polarity between sky and earth often being expressed by pairing a "Sky father" god with an "Earth mother" goddess (pairings of a Sky mother with an Earth father are less frequent). A main sky goddess is often the "queen" ("of heaven", for example).
Gods may rule the sky as a pair (for example, ancient Semitic [supreme] god El and the sky goddess Asherah whom he was most likely paired with).
The following is a list of sky deities in various polytheistic traditions, by ethno-linguistic or geographic grouping.