Io

Io

6 min read

MythologyBefore ChristGreek Antiquity, mythology transmitted by the archaic and classical poets (accounts by Aeschylus and Ovid)

Io is a figure from Greek mythology, a priestess of Hera and daughter of the river-god Inachus. Loved by Zeus, she was transformed into a heifer and pursued across the world by Hera's jealousy before regaining her human form in Egypt.

Frequently asked questions

Io is a central figure in Greek mythology, a priestess of Hera at Argos and the daughter of the river god Inachus. The key thing to remember is that she is best known for having been loved by Zeus, then turned into a heifer to hide her from Hera's jealousy. Her story, told notably by Aeschylus and Ovid, is a foundational myth that connects Greece to Egypt.

Key Facts

  • Daughter of the river-god Inachus and priestess of Hera at Argos
  • Loved by Zeus, transformed into a heifer to escape Hera's wrath
  • Watched over by hundred-eyed Argus, who was slain by Hermes on Zeus's orders
  • Pursued by a gadfly across the world, she gives her name to the Ionian Sea and to the Bosphorus ('passage of the cow')
  • Taking refuge in Egypt, she becomes human again and gives birth to Epaphus, ancestor of a heroic lineage (including Heracles)

Works & Achievements

Prometheus Bound (Aeschylus) (5th c. BC)

Tragedy in which Io, driven to wander, converses with Prometheus, who foretells her destiny and her descendants.

The Suppliants (Aeschylus) (c. 463 BC)

Tragedy centered on the Danaids, descendants of Io who have returned from Egypt to Greece.

Metamorphoses, Book I (Ovid) (c. 8 AD)

The most complete Latin poetic account of Io's metamorphosis and the death of Argus.

The Library (Apollodorus) (1st–2nd c. AD)

Mythographic compilation that establishes the canonical version of the myth of Io.

Histories, Book I (Herodotus) (c. 440 BC)

A rationalized version of the abduction of Io, presented as an episode in the conflicts between Greeks and Easterners.

Attic vases depicting Io and Argus (5th–4th c. BC)

A rich iconography of Io's liberation by Hermes, attesting to the popularity of the myth.

Pompeian frescoes of Io in Egypt (1st c. AD)

Wall paintings showing Io welcomed by Isis on the banks of the Nile.

Anecdotes

In the myth, Zeus turns Io into a white heifer to hide her from his wife Hera. But the suspicious goddess demands the animal as a gift and places it under the watch of Argus of the hundred eyes, fifty of which always stayed open.

To free Io, Zeus sends Hermes to lull Argus to sleep with his music and his storytelling, then beheads him. In memory of her faithful guardian, Hera sets the hundred eyes of Argus on the tail of the peacock, her favorite bird.

Still in the shape of a heifer, Io is tormented by a gadfly sent by Hera that stings her without respite. Driven mad, she wanders across the world and crosses a strait that will take her name: the Bosphorus, literally the “passage of the cow.”

In Aeschylus's *Prometheus Bound*, Io meets the Titan crucified on his rock in the Caucasus. Two victims of divine wrath share their plight: Prometheus foretells her long wanderings and announces that one of her distant descendants will one day set him free.

Having reached Egypt, Io finally regains her human form on the banks of the Nile and gives birth to Epaphus. The Greeks identified her with the Egyptian goddess Isis, and some of her descendants, such as Danaus, would later return to settle in Greece.

Primary Sources

Aeschylus, Prometheus Bound (5th century BC)
A gadfly stings me, a goad forged without fire; it pursues me with its assaults. Gripped by terror, my heart leaps and pounds against my chest.
Ovid, Metamorphoses, Book I (around 8 AD)
The god strips her of her beauty and turns her into a heifer; even in this form, she remains lovely. Argus of the hundred eyes guards her, and a part of his eyes was always watching.
Aeschylus, The Suppliants (around 463 BC)
We glory in being descended from Io, the cow beloved of Zeus, who once wandered across this land, tormented by the gadfly.
Apollodorus, Library, Book II (1st–2nd century AD)
Zeus, caught with Io, transformed her into a white heifer. Hera asked for her and set as her guardian Argus, whose body was covered with eyes.

Key Places

Argos

City in the Peloponnese where Io was a priestess at the sanctuary of Hera (the Heraion). It is her homeland and the starting point of the myth.

Bosphorus

Strait linking the Black Sea to the Sea of Marmara, crossed by Io in the form of a heifer. Its name means “the ford of the cow.”

Caucasus

Mountain range where Prometheus is chained; Io meets him there during her wanderings and receives his prophecies.

Ionian Sea

Sea lying to the west of Greece, which tradition holds was named after Io's wanderings.

Egypt (Nile Valley)

The end of Io's journey, where she regains her human form on the banks of the Nile and gives birth to Epaphus. The Greeks identified her there with Isis.

See also