daughter of the Argivian king Inachos, and one of Zeus's mistresses, who the
god had turned into a cow to avoid the wrath of Hera. When Hera realized who
the cow was, she made the monster Argus guard her until Zeus sent Hermes to
rescue her. Hera kept persecuting Io in the shape of a gadfly, who swam to
Egypt, where she turned into a nymph again and gave birth to Heracles ancestor
The Ionian sea was named after her since she swam across that sea on her way to Egypt. Io's father was the river god Inachus.
According to Herodotus, Io was in reality a Greek princess who was kidnapped by the Phoenicians.