The Hydra, often referred to as the Lernaean Hydra, was a multi-headed swamp-dwelling serpent from the Peloponnese region of modern-day Greece.

The foul monster’s parents were Echidna, sometimes known as the mother of all monsters, and Typhon, another serpent-like creature that declared war on Zeus, god of the Olympians. Hydra lived in a spring at Amymone, not far from Argos, where it terrorized the countryside of Lerna.

The Hydra initially had nine heads, but subsequent sources have put the number of its heads at anything from two to 100. However, this might not seem odd if we consider that the monster could regrow a head if it were cut off. Therefore, it’s logical that the creature could have a contrasting number of heads at any given time. Some sources have given the Hyrda a double or split tail, which, just like the heads, could regenerate. Hydra is mainly referred to in literature as an “it” but sometimes is gendered female. Artistic representations often portray the Hydra with human female features in the face and torso.

Known Hydra literature begins in 8th Century BC

The oldest narrative of Hydra appears in Hesiod’s poem, Theogony, written circa 730–700 BC. Hesiod explains that Hydra was the third creature born to Echidna and Typhon but was reared by the Olympian goddess Hera. The goddess later pitted Heracles against the creature in the second test of his twelve labors.

Hesiod wrote,

Then [Echidna] bore foul-minded Hydra of Lerna,
reared by the white-armed goddess Hera when
she was monstrously angry with mighty Heracles.
But Heracles, son of Zeus and of Amphitryon,
slew the Hydra with pitiless bronze, aided
by warlike Iolaus and plunderer Athena’s counsel.

Hydra is best known for its fight against Heracles, and further appearances in Greek and Roman literature primarily revolve around this battle.

The story of Heracles’ battle with the Hydra

Heracles enlisted the help of his nephew, Iolaus, to slay the Hydra, and the pair rode a chariot toward the spring of Amymone, where Heracles spotted the nine-headed serpent on a hill just before it vanished into its den. According to Pseudo-Apollodorus, writing in the 2nd century BC, Heracles pelted the den with fiery shafts, forcing the monster to come out and grab the Greek hero by the legs. Heracles and Iolaus attacked the creature with a selection of weapons, including bows and arrows, swords, clubs, and Heracles’s bespoke sickle sword. Unfortunately, whenever the two heroes lopped off or destroyed one of the Hydra’s heads, another two grew back in its place.

Heracles devised an ingenious solution: When he cut off a head, Iolaus quickly applied a burning brand to the wound, cauterizing the severed stumps and preventing another head from reappearing. The final head was immortal, but Heracles solved that problem by lopping it off and burying it under a rock beside the road from Lerna to Elaeus.

Heracles then chopped up the Hydra and dipped his arrows in the monster’s blood, which had the effect of poisoning them, meaning any wounds inflicted by them were incurable. In another version of the story, Heracles dipped his arrows into the Hydra’s severed head, transferring its venom to the arrows. This act would later come back to haunt Heracles when his wife, Deianeira, accidentally killed him with the same poison. It also led to the death of the centaur Chiron, teacher of Achilles, after Heracles accidentally shot him with a poisoned arrow.

Unfortunately for Heracles, Eurystheus, who set the hero his twelve labors on behalf of Hera, ruled that his victory over the Hydra did not count because he had the help of Iolaus.

Hera was allegedly upset by Heracles’s victory and placed Hydra in the stars as the constellation Hydra. During the battle, a crab had emerged from the swamp and attempted to assist the Hydra by capturing Heracles’s foot in its claws. However, Heracles simply crushed it with the heel of his foot. Hera, as a sign of her gratitude, placed the crab in the stars, where it became the cancer constellation.

Pseudo-Apollodorus began his tale of the battle with the following description of Hydra:

“As a second labor [Eurystheus] ordered [Heracles] to kill the Lernaean hydra.3 That creature, bred in the swamp of Lerna, used to go forth into the plain and ravage both the cattle and the country. Now the hydra had a huge body, with nine heads, eight mortal, but the middle one immortal.”

The Hydra features heavily in Greek and Roman mythology

The Hydra has appeared in numerous literary works from Greek and Roman authors and beyond. The creature was referenced in the work of Ovid, Senecan, Virgil, and many other Roman literary giants.

Writing in the 2nd century AD, Greek geographer Pausanias wrote in his work, Description of Greece, that he believed a powerful and poisonous serpent lived at the source of Amymone in Lerna Lerna, but he doubted it could regenerate heads.

Pausanias wrote:

“At the source of the Amymone grows a plane tree, beneath which, they say, the [hydra] water-snake grew. I am ready to believe that this beast was superior in size to other water-snakes, and that its poison had something in it so deadly that Heracles treated the points of his arrows with its gall. It had, however, in my opinion, one head, and not several. It was Peisander of Camirus who, in order that the beast might appear more frightful and his poetry might be more remarkable, represented the hydra with its many heads.”

The first known artistic representation of Hydra appeared around the same time as Hesiod’s writings on a pair of 8th-century BC bronze fibulae (brooches.) The artwork featured Heracles battling a six-headed Hydra with the help of Iolaus, and even the crab made an appearance beneath Heracles’s legs. Since then, the fight has featured on numerous vases, mosaics, and other items.

The word hydra comes from the Greek word for a water snake.

Much like many of the monsters found in ancient Greek literature, Hydra’s true origin may come from a different region entirely. The Sumerian epic poem The Return of Ninurta to Nippur, often known simply as Angim, tells the tale of the Mesoptamian God Ninurta, who returned triumphantly from a hunting trip with an array of slain animals and monsters, including a seven-headed serpent.


Original sources

Apollodorus. “The Bibliotheca,” This version published 1921 and trans. by James George Frazer. Pub.: W. Heinemann, accessed May 6, 2024.

Hesiod, “Theogony,” translated by Michael Heumann (2021), accessed May 6, 2024.

Pausanias. “Description of Greece,” Translators: Henry Arderne Ormerod, William Henry Samuel Jones, (1918), Pub.: Harvard University Press, accessed May 10, 2024.

Secondary sources

Britannica.com, “Hydra: Greek Mythology,” accessed May 10. 2024.

Ogden, Daniel. “Drakon: Dragon Myth and Serpent Cult in the Greek and Roman Worlds,” Pub.: OUP Oxford, (2013), accessed May 6, 2024.

Perseus Digital Library, “The Lernean Hydra,” accessed May 10, 2024.

Theoi Greek Mythology, “Hydra Lernaea,” accessed May 7, 2024.

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