The Nemean Lion was a monster in Classical Greek mythology. The Nemean Lion had the appearance of a normal lion but was incredibly strong. One swipe from its paws was able to kill a man. On top of this, its skin acted as armor that no man-made weapon could pierce.
The Nemean Lion was the fearsome offspring of Typhon and Echidna, and participated with them in the battle against the Gods. When Typhon was defeated by Zeus, the Nemean Lion, along with its siblings Cerberus, Chimaera, Sphinx, the Lernaean Hydra, Ladon, and Orthus were allowed to live to pose challenges to future heroes.
The Nemean Lion was defeated by Heracles as the first of his Twelve Labors. Since the Nemean Lion's skin was impenetrable, Heracles chased it from its lair, bashed it with his club, and strangled it to death. He then skinned it with its own claw and used the skin as an impenetrable coat of armor that protected him in his later labors.
The name Nemean Lion refers to the city, Nemea, near which the beast made its lair as appointed by Hera, who's fury towards Zeus's extramarital affairs was renowned. Heracles was a bastard son of Zeus, and Hera wanted to arrange a task Heracles would be bound to fail.