The Nemean lion (//; Greek: Νεμέος λέων Neméos léōn; Latin: Leo Nemeaeus) was a vicious monster in Greek mythology that lived at Nemea. It was eventually killed by Heracles. It could not be killed with mortals' weapons because its golden fur was impervious to attack. Its claws were sharper than mortals' swords and could cut through any armor. In Bibliotheca, Photius wrote that the dragon Ladon, who guarded the golden apples, was his brother.
Today, lions are not part of the Greek fauna. The Asiatic lion subspecies formerly ranged in southeastern Europe. According to Herodotus, lion populations were extant in Ancient Greece. George Schaller asserts that they may have been present in the area until circa 100 BC.
Hesiod has the Nemean lion as the offspring of Orthus, and an ambiguous "she", often understood as probably referring to the Chimera, or possibly to Echidna, or even Ceto. According to Hesiod, the lion was raised by Hera and sent to terrorize the hills of Nemea. According to Apollodorus, he was the offspring of Typhon. In another tradition, told by Aelian (citing Epimenides) and Hyginus, the lion was the child of the moon-goddess Selene, who threw him from the moon at Hera's request.
Heracles wandered the area until he came to the town of Cleonae. There he met a boy who said that if Heracles slew the Nemean lion and returned alive within 30 days, the town would sacrifice a lion to Zeus; but if he did not return within 30 days or he died, the boy would sacrifice himself to Zeus. Another version claims that he met Molorchos, a shepherd who had lost his son to the lion, saying that if he came back within 30 days, a ram would be sacrificed to Zeus. If he did not return within 30 days, it would be sacrificed to the dead Heracles as a mourning offering.
While searching for the lion, Heracles fetched some arrows to use against it, not knowing that its golden fur was impenetrable; when he found the lion and shot at it with his bow, he discovered the fur's protective property when the arrow bounced harmlessly off the creature's thigh. After some time, Heracles made the lion return to his cave. The cave had two entrances, one of which Heracles blocked; he then entered the other. In those dark and close quarters, Heracles stunned the beast with his club. He eventually killed the lion by strangling it with his bare hands.
Finally, Athena, noticing the hero's plight, told Heracles to use one of the lion's own claws to skin the pelt.
When he returned on the thirtieth day, carrying the carcass of the lion on his shoulders, King Eurystheus was amazed and terrified. Eurystheus forbade him ever again to enter the city; in the future, he was to display the fruits of his labours outside the city gates. Eurystheus warned him that the tasks set for him would become increasingly difficult. He then sent Heracles off to complete his next quest, which was to destroy the Lernaean Hydra.
Heracles wore the Nemean lion's coat after killing it, as it was impervious to the elements and all but the most powerful weapons. Others say that Heracles' armour was, in fact, the hide of the Lion of Cithaeron.
According to Alexander of Myndus, Heracles was helped in this labour by an Earth-born serpent, which followed him to Thebes and settled down in Aulis. It was later identified as the water snake which devoured the sparrows and was turned into stone in the prophecy about the Trojan War.
Chronological listing of classical literature sources for the Nemean Lion: