Gilgamesh, the son of a man and a goddess, is king of the ancient Sumerian city-state of Uruk. Oh, and he's also the strongest and most handsome man in the world. Must be nice.
Unfortunately, Gilgamesh's assets have gone to his head, and he spends all his time wearing out the young men of the city with endless athletic contests and sexually exploiting the young women. When the citizens of Uruk can't take it anymore, they pray to the gods for help. The god Anu hears them, and commands the goddess Aruru to create another human who will be a match for Gilgamesh.
Aruru creates Enkidu, an uncivilized wild man, and places him in the woods. There, Enkidu has several run-ins with a trapper who uses the same watering hole. Terrified, the trapper goes to Uruk for help. On Gilgamesh's advice, the trapper goes back to the watering hole with Shamhat, a temple-prostitute. When Enkidu shows up, Shamhat entices him to have sex with her.
Afterward, Enkidu finds that he can no longer keep up with the animals, but that his mind has been opened. He starts living with Shamhat, who initiates him into human life. When she mentions Gilgamesh, Enkidu realizes that he wants a friend—and that he wants to give Gilgamesh a beat-down. (Frenemies!) Oh, what a coincidence—Gilgamesh has been dreaming about getting a new friend, too.
Soon enough, Enkidu goes to Uruk and faces down Gilgamesh. Gilgamesh wins, natch, but there are no hard feelings, and the two warriors become best buds.
One day, Gilgamesh decides to go to the distant Cedar Forest and kill Humbaba, the monster who guards it. Because, you know, why not? Against the advice of the elders of Uruk and Enkidu himself, the two friends set out on their quest. Once they make it to the Cedar Forest, the sun god Shamash helps them overpower Humbaba, who starts pleading for mercy. Gilgamesh is about to grant it, but then gives in to peer pressure from Enkidu, and kills him. (Just say no, you guys.)
The friends cut down the tallest tree in the forest, which Enkidu plans to dedicate to the god Enlil. They build a raft and sail home down the River Euphrates, taking Humbaba's head along for the ride. Fun!
At this point, the goddess Ishtar develops a crush on Gilgamesh and asks him to marry her. Gilgamesh rejects her, pointing out that all of her previous lovers have come to bad ends. Seriously pissed off, Ishtar borrows the Bull of Heaven from her dad, Anu, and sends it to earth to punish the friends. But they kill the Bull, and, when Ishtar appears on the ramparts of Uruk, Enkidu throws one of its legs in her face.
Not long afterwards, Enkidu dreams that the gods have decided that, for killing Humbaba, chopping down the cedar, and killing the Bull of Heaven, either he or Gilgamesh must die—and that Enlil picked Enkidu. In no time, Enkidu falls mysteriously ill, and dies after much suffering.
Gilgamesh is majorly bummed. Finally, he decides to travel beyond the ends of the earth to speak to Utanapishtim, the one human who has been granted immortality. An exhausting journey brings Gilgamesh to Mount Mashu, where two scorpion-beings guard the rising of the sun. Allowed to continue, Gilgamesh makes a harrowing journey to the underside of the world, barely avoiding being burned to a crisp by the sun.
Upon arrival, he meets Siduri the innkeeper, who directs him to Urshanabi the ferryman. Despite getting a bad first impression, Urshanabi helps Gilgamesh cross the Waters of Death. On the other side, Gilgamesh meets Utanapishtim, who tells him, "Tough luck: humans just can't escape death."
See, long ago, the gods decided to destroy all of humanity with a Flood. But he and his wife got some advance warning from the god Ea, and built a giant ship, on which they stored all kinds of living creatures, as well as some craftsmen. When the Flood was over, the god Enlil granted Utanapishtim and his wife immortality. Utanapishtim doesn't think Gilgamesh is worthy of such a gift; to prove it, he challenges our hero to a staying-awake contest.
Gilgamesh fails miserably. (We feel you, Gil. We fail our staying-awake contests every night.) Utanapishtim tells him to take a hike, and fires Urshanabi for good measure. After those two sail off, however, Utanapishtim's wife makes her husband call them back. This time, Utanapishtim tells Gilgamesh about a plant that will restore the youth of whoever eats it.
Gilgamesh finds the plant on the bottom of the sea and decides to take it home to Uruk and test it on an old man. (Wise—try it on someone else, first.) At the first rest stop on the way home, Gilgamesh takes a bath and leaves the flower on the ground. A snake comes by and eats the flower. D'oh! Unperturbed, Gilgamesh and Urshanabi keep journeying toward Uruk. When they reach it, Gilgamesh boasts about the city's architecture, echoing the opening of the poem