In Genesis, a rainbow is the sign of the covenant after Noah’s Flood.
Genesis 9:12–17 describes a covenant between God and Noah, his descendants, and every living creature. The rainbow in the clouds is presented as the visible sign of that promise. The covenant states that the waters will not again become a flood destroying all flesh.
The passage places the rainbow after Noah leaves the Ark and builds an altar. It is therefore a post-Flood covenant sign, not a feature used to guide the Ark during the storm.
The rainbow has acquired many meanings in later religious, cultural, and artistic traditions. In the Genesis account, its specific narrative function is remembrance of the covenant concerning the earth and living creatures. The text also repeats the promise in connection with future clouds and waters.