Stories about a great flood are found in the folklore of many cultures. The earliest written sources are inscribed in Sumerian on clay tablets and date to the late third millennium B.C. Mesopotamian versions of the flood story may have had their beginnings in the annual spring flooding of the Tigris and Euphrates rivers. Alternatively, some scholars believe that a change in the ancient sea level in the Persian Gulf may have given rise to stories about a deluge.
The Sumerian King List, a literary composition existing in several different versions, traces kingship from its origins to contemporary dynasties that ruled in southern Mesopotamia between the twenty-first and nineteenth centuries B.C. According to this composition, eight legendary rulers reigned for a combined total of 241,200 years, "then the flood swept over." Ubara-tutu, from the city of Shuruppak, noted as the last prediluvium monarch in the King List, is mentioned by other names in several later flood stories. In one of these tales, called the Sumerian Flood Story by modern scholars (the ancient name is not preserved) and dating to the Old Babylonian period but possibly composed in the third millennium B.C., the gods fashion the black-headed people (the Sumerians) and create animals which multiply all over the earth. Later, after they have chosen a human king, rites are performed and cities founded. When Ziudsudra ("Life of Distant Days") is king, he hears a message from a god saying that a flood will sweep over the land. The gods in their divine assembly have made an irrevocable order to destroy mankind. After a break in the text, the wind and gales blow and the flood sweeps over the land. The storm rages for seven days and seven nights while Ziusudra, "the seed of mankind," and animals ride it out in a sealed boat. Finally, the flood over, Ziusudra drills an opening in the boat and the sun enters. Once on firm ground, the animals disembark and the hero sacrifices oxen and sheep. The god Enlil then appears and treats Ziusudra kindly. He is given eternal life like a god and settles in the land of Dilmun, a place at the end of the earth where the sun rises.
Another Sumerian tale, "The Death of Bilgamesh" ("The Great Wild Bull Is Lying Down"), preserved in a copy dating to the Old Babylonian period, contains a section in which the gods review the life and career of the hero Bilgames (Gilgamesh in Akkadian). They describe how the hero fought the ogre Huwawa in the Cedar Forest and how he traveled to meet Ziusudra in his "abode" and learned about the deluge. The gods inform him that in spite of the fact that his mother was a goddess, he is mortal like all humans and will eventually take his place with the dead in the underworld.
Students at the academies during the Old Babylonian period also recorded a Babylonian story about a hero named Atra-hasis that contains a flood narrative. The narrative begins with an account of the early history of humankind. When the gods create humans to ease their burden in forming the world, they mistakenly forget to limit men's and women's years on earth. Consequently, humans multiply to such an extent that the noise they create becomes overwhelming and the god Enlil, the head of the pantheon, cannot sleep. Enlil believes that the only way to control this surge in population is by a plague, but when the plague god is presented with offerings, he relents and the plague ends. Soon after, the human population begins to multiply anew. When Enlil's next attempt to limit humankind's growth by the introduction of famine fails, he orders a flood to destroy all peoples. Atra-hasis is warned by Enki, the god of wisdom, of the impending disaster. He is advised to build a boat and save both his kin and animals. The storm rages for seven days and nights. After it subsides, Atra-hasis emerges from the ark and prepares an offering for the gods. When Enlil becomes aware that his plan to destroy all living beings has failed, he asks, "How did man survive in the destruction?" Enki responds and accuses Enlil of overreacting to the population explosion: "Instead of bringing about a flood, lions and wolves should have appeared and diminished the people . . Impose the penalty on the guilty. Impose the crime on the criminal. Henceforth let no flood be brought about, but let the people last forever." Enlil agrees and tells the flood hero that only he and his wife shall henceforth be granted eternal life. From now on, Enlil continues, human lifespan will be numbered and human population controlled though the creation of special classes of women who will bear no children. In addition, he decrees that some babies will be snatched from the laps of their mothers by pashittu-demons.
An expanded version of the flood story is found in the 11th Tablet of the Babylonian Gilgamesh epic. Here, the legendary Uta-napishtim, son of Ubara-tutu, relates a tale about the great deluge. Warned by the god Ea (Sumerian: Enki) that the great gods have decided to send down a flood to destroy humankind, Ea instructs Uta-napishtim to demolish his house, abandon wealth, build a boat, and seek safety. He is to take on board the boat the seed of all living things. The boat is to be six decks high and shaped like a cube. Uta-napishtim obeys his god; he loads the boat with all of his gold and silver and takes on board the beasts of the field and the creatures of the wild together with artisans and all of his family and kin. Soon the storm begins; for six days and seven nights, the wind blows and the deluge flattens the land, but on the seventh day the ocean grows calm and the boat runs aground on a mountain. Seven days later, Uta-napishtim lets loose a dove to find land, but the dove returns. Next he dispatches a swallow, but it too comes back. Finally, a raven is set free and never returns. Disembarking from the boat, Uta-napishtim makes an offering to the gods, but when the god Enlil smells the smoke and sees the boat, he is seized with fury. However, reprimanded by Ea for his lack of foresight and reason, Enlil relents and declares that Uta-napishtim and his wife shall become immortal and dwell far away at the source of the rivers.
Two other ancient Near Eastern flood stories from beyond the borders of Mesopotamia are known, the most famous being the version found in the book of Genesis. Another short but very fragmentary version describing only Atra-hasis, the flood itself, and the conclusion that the hero gains immortality was found at ancient Ugarit and dates to the fourteenth century B.C.
A much later version of the flood story was written in Greek by Berossos, a Babylonian priest of the god Bel. This tale, part of a larger work on Babylonian history, is lost, but sections of the flood story are quoted by the later Greek writers Eusebius and Polyhistor. According to this version of the tale, the hero Xisuthros (Ziusudra) has a dream in which the god Kronos warns him about the onslaught of an impending flood. Xisuthros digs a hole and buries all the written material from his city. Then he builds a boat "five stades long and two stades wide" and boards his wife, children, and closest friends. After the flood subsides, Xisuthros lets loose birds who return to the ship empty-handed. A few days later, he again frees birds and they return with their feet covered in mud. When he releases birds for a third time, they fail to return. The boat having landed in the mountains of Armenia, Xisuthros disembarks, offers a sacrifice to the gods, and disappears to dwell with the gods together with his wife and daughter. When the rest of his party leaves the boat, they hear a voice from afar instructing them to return to worship the gods, dig up the writings buried in Sippar, and establish Babylon.