The Genesis flood narrative makes up chapters 6–9 in the Book of Genesis, in the Bible. As one of many flood myths found in human cultures, the narrative recounts God's intent to return the Earth to its pre-creation state of watery chaos by flooding the Earth because of humanity's misdeeds and then remake it using the microcosm of Noah's ark. Thus, the flood was a reversal of creation. The narrative discusses the evil of mankind that moved God to destroy the world by the way of the flood, the preparation of the ark for certain animals, Noah, and his family, and God's guarantee (the Noahic Covenant) for the continued existence of life under the promise that he would never send another such flood.
Although many religious groups consider the story to be largely allegorical, there are still many groups and individuals who believe the story to be literally true. Since at least the 19th century, scholarly consensus has been, and evidence from scientific investigation has shown, that the story cannot be literally true, and among scholars it is categorized along with other flood myths as a legend.
Genesis 6:1–4 presents the reason for the flood: the Sons of God marry the daughters of men and sire a race of giants, "mighty men which [were] of old, men of renown". Genesis continues: "And GOD saw that the wickedness of man [was] great in the earth, and [that] every imagination of the thoughts of his heart [was] only evil continually." (Genesis 6:5) God decides to destroy the world in a reversal of creation.
The flood occurs because God judges humanity. In Genesis 6:5-8, the LORD judged "man" for being wicked and evil. In verses Genesis 6:11-22, God judged "all flesh" for being corrupt and violent. The judgment in verses 6:5–8 is thought to have been written earlier and later combined with the second. This element of judgment makes the flood story different from the flood in the Babylonian Epic of Gilgamesh. In the Gilgamesh story, the flood is mentioned only in passing as part of the Epic tale itself, and appears to have been the result of polytheistic caprice, not the supreme God's moral judgment. However, in the Atrahasis version of the Babylonian flood story (which deals directly with the flood), it is made clear that the flood was sent by the gods to reduce human over-population, and after the flood other measures were introduced to prevent the problem recurring.