In Greek mythology, Cephissus or Kephisos (Ancient Greek: Κηφισός) is a river-god associated with the Cephissus of Attica and/or the Cephissus of Boeotia. Genealogies make him son of Pontus and Thalassa and father of several eponymous nymphs and of Narcissus by the naiad Liriope. An Argive river-god of the same name, with Inachus and Asterion, judged Argolis for Hera against Poseidon and was punished by drought.
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I.Family
Cephissus was a son of Pontus and Thalassa. His daughters include the naiad Lilaea (eponym of Lilaea), Daulis (eponym of Daulis), and Melaeno, mother of Delphus by Apollo in one account; Thyia, to whom the Delphians built an altar of the winds, is also called his daughter by Herodotus. A mortal son Eteocles (or Eteoclus), by Euippe daughter of Leucon, was the first to offer to the Charites beside the Cephissus, according to Hesiod and Pindar. Ovid, Hyginus, and Statius make him father of Narcissus by the naiad Liriope; another son, Euonymus, fathered Aulis, eponym of Aulis.
II.Mythology
The same name attaches to an Argive river-god who, with Inachus and Asterion, judged that Argolis belonged to Hera rather than Poseidon; the sea-god made their waters vanish, so that none of the three rivers waters the land except after rain. In an obscure myth Cephissus greatly lamented a grandson turned into a seal by Apollo.
A late-fifth-century BC Attic votive relief (the Xenokrateia Relief) commemorates the founding of a sanctuary to Cephissus and is now in the National Archaeological Museum of Athens.