Io, in Greek mythology, daughter of Inachus, king ofo Argos. She was loved by Zeus, who, to protect her from Hera's jealousy, changed her into a white heifer. Hera, however, was not deceived; she claimed the heifer and sent Argus to guard it. When Hermes killed Argus, Hera tormented Io with a gadfly which drove her across Europe and through Asia, until she was finally allowed to rest in Egypt. There Zeus returned her to human form, and she bore his child Epaphus. Io has been identified with the Egyptian goddess Isis.
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