Myths and Folklore Wiki

The Lernaean Hydra or Hydra of Lerna (Greek: Λερναῖα Ὕδρα, Lernaîa Hýdra), more often known simply as the Hydra, is a serpentine water monster in Greek and Roman mythology.  

Its lair was the lake of Lerna in the Argolid, which was also the site of the myth of the Danaïdes. Lerna was reputed to be an entrance to the Underworld, and archaeology has established it as a sacred site older than Mycenaean Argos. In the canonical Hydra myth, the monster is killed by Heracles (Hercules) as the second of his Twelve Labors. 

Myths & Legends[]

Various sources have suggested that the Hydra first appeared (in writing and on art) between c 600-700 BE. 

It's most distinctive characteristic was the multiple heads. Each time a head was cut off, two new heads regenerated in its place immediately (though there are some variations in this number depending on the writer). The middle and dominant Hydra head (the front and biggest) was immortal and breathed fire. This giant serpent’s other heads possessed poisonous breath in addition to poisonous and acidic blood. Even its scent was deadly/ 

Hercules would later use this poisonous/acidic blood to defeat other creatures. These included the Stymphalian Birds, the giant Geryon, and the centaur Nessus which ruined the river Anigrus.


The Hydra (also known as the Lernaean Hydra) was a Greek mythological serpent with any number of heads (usually nine, but the original number of heads varies depending on author). It is usually depicted as being from anywhere between 7 and 25 meters long and being around 6 to 13 meters tall. This is not correct or incorrect as the hydra is usually fought at different stages of its life depending on the version of the legend. The Hydra is usually often referred to as a female in myth as well. 

The Second Labor of Heracles[]

Hercules was sent by king Eurystheus to kill the Hydra as part of his second labor since the Lernean Hydra was terrorizing Lerna by attacking it is towns and killing flocks of sheep and cattle. Hera had raised this monster just to slay Heracles.

He had taken along his nephew Iolaus. When they reached Lerna, he protected his nasal area and mouth with a fabric to safeguard himself from the stench. He shot a flaming arrow into its cave where it hissed in anger, arrived and started fighting him.

However, he had trouble coping with the Hydra when he understood that two heads regenerated whenever he sliced away one head. He informed Iolaus to cauterize the neck stumps with fire whenever Hercules cut its heads off to be able to stop the heads regrowing. An alternate version of this myth is that after cutting off one head he then dipped his sword in its neck and used its venom to burn each head so it could not grow back.

When Hera saw Hercules was winning, she sent down a huge crab called Korkinos to attack him by pinching his foot which he then crushed under his mighty foot.

He received a golden sword from Athena, which he utilized to finally kill the last head of the beast. The Hydra's one immortal head was cut off with a golden sword given to Heracles by Athena. Heracles placed the head—still alive and writhing—under a great rock on the sacred way between Lerna and Elaius, and dipped his arrows in the Hydra's poisonous blood. Thus his second task was complete. However, as Hercules' nephew Iolaus assisted in this trial, Hera also decided that the trial didn't count as one of the 10 trials required.

Hera, upset that Heracles had slain the beast she raised to kill him, placed it in the dark blue vault of the sky as the constellation Hydra. She then turned the crab into the constellation Cancer.

Similar Creatures in other Regions[]

The Hydra had many parallels in ancient Near Eastern religions.

  • In particular, Sumerian, Babylonian, and Assyrian mythology celebrated the deeds of the war and hunting god Ninurta, whom the Angim credited with slaying 11 monsters on an expedition to the mountains. One of these monsters was a seven-headed serpent that could potentially be the Mušḫuššu whose constellation (despite having a single Head) was later associated by the Greeks with the Hydra.
  • In Japanese mythology, Yamato no Orochi was an eight-headed serpent.


Greek and Roman writers related that Hera placed the Hydra and crab as constellations in the night sky after Heracles slew him. When the sun is in the sign of Cancer (Latin for "The Crab"), the constellation Hydra has its head nearby. In fact, both constellations derived from the earlier Babylonian signs: Bashmu ("The Venomous Snake") and Alluttu ("The Crayfish").


Image gallery of Lernaean Hydra


  • The hydra does not already have a set number of heads because the hydra had way too many heads for the vase painters to paint so they always gave it between 3 and 20 heads. Under normal circumstances the hydra never has less than 3 heads.
  • The hydra is usually depicted as having either two arms and no legs, two arms and two legs or no arms or legs at all when the hydra actually starts off with having no legs then it develops two arms then two legs. So all of these depictions are partially correct.
  • There are often 2 kinds of hydra. The serpentine, aquatic hydra with fins on its head and usually no legs was the lernean hydra which Heracles fought. The other is the terrestrial hydra which is the one with 4 legs and horns and spikes which is usually in other tales.
  • Both of these hydra's could have any number of heads and does not have a set amount.