Gilgamesh is the Priest-King of the city of Uruk. He is a tyrannical king who works his people to death and takes what he wants from them. He kills the young men at will and uses the women as he pleases. The people of Uruk cry out to the gods for help so that they can have peace.
The gods hear them and instruct Anu, the goddess of creation, to make a twin for Gilgamesh, someone who is strong enough to stand up to him and who will ultimately save him. Anu makes Enkidu, a hairy wild man who lives in the wilderness with the animals.
One day a trapper sees Enkidu by a water hole and is frightened. He tells his father of the wild man he saw. His father tells the trapper to go to see Gilgamesh. He tells his son to ask the king for a temple prostitute to bring back with him to seduce Enkidu. The trapper returns with Shamhat, a temple prostitute from the temple of Ishtar, the goddess of love and war. They wait for Enkidu to reappear by the watering hole.
Enkidu returns and Shamhat reveals herself to him. They copulate for six days and seven nights. When Enkidu is satisfied, he finds that the animals no longer accept him. Shamhat tells him to come back with her to Uruk. Upon hearing of Gilgamesh, Enkidu decides he wishes to meet him. The two set out for Uruk, making a stop at a shepherd's camp. There Enkidu learns that Gilgamesh will sleep with a newly married bride on her wedding night, before her husband sleeps with her. He is outraged and decides he must stop Gilgamesh. Meanwhile, Gilgamesh has several dreams foretelling the arrival of Enkidu.
The two meet in the streets of Uruk and a great fight breaks out between them. Gilgamesh is triumphant but his encounter with Enkidu changes him. They become companions. Enkidu tells Gilgamesh of Humbaba, a terrible monster who guards the Cedar Forest. Gilgamesh decides the two of them should journey there and defeat the monster.
They make preparations and head to the Cedar Forest. They encounter Humbaba and with the help of Shamash, the sun god, defeat him. They return to Uruk carrying his head. After a celebration, Gilgamesh bathes himself and catches the eye of Ishtar. She tells him to become her lover, promising great riches and rewards in return. Gilgamesh rejects Ishtar, telling her he is aware of her reputation as a scornful lover.
Ishtar is outraged and convinces her father, Anu, to release the Bull of Heaven to punish Gilgamesh. The Bull of Heaven descends on Uruk, killing hundreds of men. Enkidu seizes the animal and Gilgamesh kills it with a sword. Ishtar appears and threatens the heroes. Enkidu tears off one of the Bull's haunches and throws it at Ishtar. Later that night, Enkidu has a dream that the gods are meeting in council.
The dream proves true. The gods decide that one of the heroes must die for their behavior. They choose Enkidu. Enkidu falls ill and suffers for twelve days before finally dying. Gilgamesh is shattered. He mourns for days and tears his hair and clothes. He adorns filthy animal skins and journeys into the forest and mountains. He has witnessed death and is now terrified of his own mortality. He seeks to escape it.
Gilgamesh decides to seek out Utnapishtim, the one being granted immortality by the gods. He travels to Mount Mashu, a twin-peaked mountain that marks an entrance to a world in which mortals cannot venture. He convinces the guards of the mountain, two Scorpion-man beings, to allow him to enter a long passage under the mountain. He endures this terrible darkness for a full day.
When he emerges on the other side, he is in a wondrous paradise. He sees a tavern by the sea and approaches it, frightening its owner, Siduri, with his appearance. Siduri allows him to enter the tavern after he explains his story and his intention to find Utnapishtim. Siduri tells Gilgamesh of Urshanabi, the boatman, who can ferry Gilgamesh across the Waters of Death to where Utnapishtim resides.
Gilgamesh finds Urshanabi and the two set out to find Utnapishtim. They reach a shore and Gilgamesh meets an old man. Gilgamesh explains that he wishes to attain immortality. The old man is Utnapishtim, who tells Gilgamesh that immortality is for the gods alone. Mortals must learn to accept death. He tells Gilgamesh the story of how he was granted immortality by the gods. He asks Gilgamesh what he has done to deserve this same gift.
Gilgamesh finally leaves with Urshanabi to return to Uruk. Utnapishtim tells Gilgamesh of a magical plant at the bottom of the sea that can restore one's youth. Gilgamesh descends into the waters and retrieves the plant.
On his way back to Uruk, Gilgamesh stops to bathe in a spring, leaving the plant by the water. A serpent appears and steals the plant, leaving Gilgamesh weeping by the water's edge. He returns to Uruk with Urshanabi. Upon seeing the great city, Gilgamesh understands that it is his legacy, and that if he rules well, it will be his greatest legacy. Gilgamesh comes to understand that the most important thing in life is to have lived and loved well.