In the Epic of Gilgamesh, a serpent steals the plant that can restore youth.
Utnapishtim tells Gilgamesh about a plant growing at the bottom of the sea. Gilgamesh obtains it by tying stones to himself and diving into the depths. He does not immediately consume the plant; instead, he plans to test it on an old man before using it himself.
While Gilgamesh is bathing in a pool, a serpent smells the plant, takes it, and sheds its skin as it departs. Gilgamesh realizes that the chance to renew his youth has disappeared. The episode helps explain the traditional association between snakes and renewed skin, although the epic itself does not make the serpent immortal.
The plant is often called a “plant of rejuvenation” in modern translations, but it has no single universally fixed English name. The important point is that Gilgamesh loses it through the serpent’s theft, not because he eats it.