Who is Io in Greek mythology?

In Greek mythology, Io was a mortal woman who was transformed into a heifer (a young female cow) by the god Zeus as part of a complex series of events.

Juno, Jupiter and Io by Dutch Golden Age painter Gerbrand van den Eeckhout


According to the myth, Io was a priestess of the goddess Hera (Juno in Roman mythology), the wife of Zeus (Jupiter in Roman mythology).

Zeus, known for his numerous affairs with mortal women, fell in love with Io and desired to be with her. To conceal his affair, Zeus transformed Io into a heifer to hide her from the jealous eyes of his wife Hera.

However, Hera was not easily fooled and became suspicious of Zeus’s actions. She demanded that Zeus give her the heifer as a gift, and the king of the gods had no choice but to comply.

Hermes and Argus by Spanish painter Velázquez

To prevent Zeus from visiting Io, Hera placed her under the watchful eye of Argus Panoptes, a giant with a hundred eyes.

In an attempt to free Io from her predicament, Zeus sent the god Hermes (Mercury in Roman mythology) to slay Argus. Hermes played music to lull the giant to sleep before swiftly decapitating him. In honor of Argus, Hera placed his eyes on the feathers of her favorite bird, the peacock.

Despite the rescue, Io’s troubles were far from over. To torment her further, Hera sent a gadfly to sting Io endlessly, causing her to wander in agony across the world.

This event gave rise to the term “Io” (or “Ionia”) as a poetic name for the land that encompasses the western coast of modern-day Turkey.

Mercury and Argus, by Flemish painter Jacob Jordaens, c. 1620 – Museum of Fine Arts of Lyon

Descendants of Io

Eventually, Io found her way to Egypt, where Zeus transformed her back into her human form. In Egypt, she gave birth to a son, Epaphus, who would become a significant figure in Egyptian mythology and genealogy. In turn Epaphus and Memphis, daughter of river god Nilus, gave birth to a child called Libya (Lybee).

The myth goes on to say that Libya had a romantic relationship with the god Poseidon, who was often associated with the sea. As a result of this union, Libya gave birth to twin sons named Belus and Agenor. These two sons became important figures in various Greek myths. Belus, in particular, is significant as the founder of the royal dynasty in Egypt and the ancestor of notable figures like Danaus and Aegyptus.

Some sources mention a third son named Lelex, who was also said to be the offspring of Libya and Poseidon. Lelex is often associated with the early history of Greece and is considered a legendary figure in some regional traditions.

Interestingly, some late accounts contradict the previous version and claim that Libya had a different partner. According to these accounts, Libya instead had a relationship with Zeus. In these versions, Libya became the mother of Belus, attributing his parentage to Zeus instead of Poseidon.

Io and Isis

The comparison between Io, the mortal woman in Greek mythology, and the Egyptian goddess Isis, as well as the association of her Egyptian husband Telegonus with Osiris, is a result of syncretism or the blending of different religious and mythological traditions.

In the case of Io, her myth of transformation and wanderings resonated with certain aspects of the Egyptian goddess Isis. Isis was a prominent goddess in Egyptian mythology, associated with motherhood, magic, and protection. Like Io, Isis was a nurturing and protective figure.

As a result, some ancient writers and scholars sought to draw parallels between Io and Isis, emphasizing their maternal and protective aspects, as well as their wanderings and transformative experiences.

Did you know…?

In 1614, German astronomer Simon Marius independently discovered the moons of Jupiter, which were also observed by Galileo Galilei around the same time. Marius named the four largest moons—Io, Europa, Ganymede, and Callisto—after characters from Greek mythology, specifically from the story of Zeus (Jupiter in Roman mythology) and his lovers.

Simon Marius, a German astronomer, is credited with naming one of the four largest moons of Jupiter after Io. Image: Engraving of Marius in his book Mundus Iovialis (World of Jupiter), 1614

Questions and Answers

The tale of Io is just one of the many intricate stories within Greek mythology, reflecting the complex relationships between gods and mortals and the consequences of divine love affairs. Image: Jupiter and Io by English portrait painter John Hoppner (1785) at Denver Art Museum

Why did Zeus transform Io into a heifer?

Io’s relationship with the god Zeus was one of the classic examples of a divine love affair. According to the myth, Io was a mortal woman and a priestess of the goddess Hera, the wife of Zeus. Zeus, known for his numerous extramarital affairs with mortal women, became enamored with Io and desired to be with her.

To conceal his affair from Hera, Zeus transformed Io into a heifer, a young female cow. This transformation was meant to hide her from Hera’s watchful eye.

However, Hera, who was suspicious of Zeus’s actions, demanded that he give her the heifer as a gift. Unwilling to reveal the truth, Zeus complied with Hera’s request.

How was Argus killed, and why did Hera place his eyes on a peacock’s feathers?

Io and Argus Panoptes

Io being watched over by Argos on Hera’s orders.

Argus Panoptes, also known simply as Argus, was a giant with a hundred eyes who was assigned by the goddess Hera to guard the heifer-form of Io, whom Zeus had transformed to protect her from Hera’s wrath.

Mercury About to Behead Argus by Ubaldo Gandolfi (c. 1770–1775)

To free Io from Argus’s constant surveillance, Zeus sent the god Hermes on a mission to kill Argus. Hermes, known for his cunning and swiftness, used his cleverness to lull Argus to sleep by playing his flute. As the giant’s eyes slowly closed, one by one, Hermes took the opportunity to decapitate Argus.

Mercurius and Argus by Dutch Golden Age painter Jan van de Velde (1615-1641)

After Hermes had killed Argus, Hera was deeply saddened by the loss of her loyal servant. In tribute to Argus, she placed his eyes onto the feathers of her favorite bird, the peacock. In doing so, Hera created the distinctive “eyespots” on the peacock’s tail feathers, which are still known as “eyes” or “ocelli.”

The peacock’s feathers, adorned with Argus’s eyes, became a symbol of Hera’s watchfulness and her continuing mourning for her loyal servant. It is said that the eyes on the peacock’s tail also served as a reminder to other gods and goddesses of the punishment they might receive if they betrayed Hera’s trust.

Why did Hera torment Io with a gadfly?

Hera tormented Io by sending a relentless gadfly to sting and torment her. The gadfly would constantly harass Io, causing her to wander the earth in agony, unable to find peace or rest. The constant torment of the gadfly added to Io’s suffering, making her life as a heifer unbearable.

Hera’s actions were driven by her jealousy and anger at Zeus’s infidelity. She sought to punish both Zeus and Io for their actions and used the gadfly as a means to torment and humiliate Io, a reminder of the consequences of crossing the queen of the gods.

Hera and Io by Dutch Golden Age painter Nicolaes Pietersz. Berchem the Younger (circa 1669)

How did Io return to her human form?

According to the myth, after enduring Hera’s torment as a heifer and wandering across various lands in pain, Io eventually arrived in Egypt. In Egypt, Zeus took pity on her and transformed her back into her human form, releasing her from the curse of being a heifer.

In her human form once again, Io gave birth to a son named Epaphus. Epaphus became an important figure in Egyptian mythology and genealogy, eventually becoming a significant ancestor to various royal families and legendary heroes.

Who were the descendants of Io in the myths?

Io’s descendants were illustrious and became the ancestors of several prominent kings and heroes in various regions. The genealogy of Io’s descendants connects her to several legendary figures in Greek and Egyptian mythology. Here are some of the notable descendants of Io:

  • Perseus was a hero known for slaying the Gorgon Medusa and rescuing Andromeda. He was a son of Zeus and Danaë, who was a daughter of Acrisius. Acrisius was the son of Abas, who was the son of Lynceus.
  • Cadmus was the legendary founder of Thebes and the sower of dragon’s teeth, from which the Spartoi warriors emerged. He was the son of King Agenor of Phoenicia, who was Io’s son.
  • Heracles (Hercules) was the renowned hero known for his incredible strength and his twelve labors. He was a son of Zeus and Alcmena. Alcmena was a daughter of Electryon, who was the son of Perseus.
  • Minos was a king of Crete known for his wisdom and for establishing the mythological Minotaur labyrinth. He was a son of Zeus and Europa. Europa was a daughter of Phoenix, who was the son of Agenor.
  • Lynceus was a figure with exceptional vision, capable of seeing things at a great distance. He was a son of Aegyptus, who was a son of Belus. Belus was a son of Poseidon and Libya (Io in her human form).
  • Cepheus was a king of Ethiopia and the husband of Cassiopeia. He was a descendant of Perseus and Andromeda.
  • Danaus was a legendary figure known for being the father of the Danaids, the fifty daughters who married the fifty sons of his twin brother Aegyptus. Danaus was a son of Belus.
  • Rhadamanthus was a son of Zeus and Europa. He became a wise and just judge in the underworld after his death.
  • Aegyptus was a son of Belus and a brother of Danaus. He was the father of the fifty sons who married Danaus’s fifty daughters, leading to the famous myth of the Danaids.

Is there any association between the land “Ionia” and the myth of Io?

Yes, there is a connection between the land “Ionia” and the myth of Io in Greek mythology. The name “Ionia” is indeed derived from the name Io.

After Io’s death, the myth of Io continued to be remembered, and her name was associated with different places. One such place was the region of Ionia, an ancient region located on the western coast of Asia Minor (modern-day Turkey).

However, some historical sources suggest that the name “Ionia” is believed to have derived from “Ion,” who was considered one of the sons of Apollo and Creusa (daughter of King Erechtheus of Athens) in Greek mythology.

Io in Greek mythology

Jupiter and Io by Dutch Golden Age painter Jacob Pynas at The Fitzwilliam Museum, UK

Dwelling place: Egypt, Argos

Parents: Inachus

Consort: Zeus, Telgonus

Children: Epaphus (or Munantius), Keroessa

Grandchild: Libya

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