In Greek mythology, Chaos (Greek: Χαος, Khaos, "yawning" or "gap"), also known as Aer (Greek: Αηρ, "air"), was the first being to come into existence after the creation of the universe. Shortly after her emergence, Gaea, Eros, and Tartarus followed. From Chaos sprang Erebus and Nyx. Aristophanes states that Chaos, Nyx, Erebus, and Tartarus were the first four beings to emerge after the creation of the universe and Eros was born from Chaos. After consorting with her son, Chaos and Eros produced all the birds of the sky.

According to Hesiod, Chaos was a personified deity as well as a location described as far away, underground, and "gloomy". Ovid describes Chaos in his poetry as an unformed mass with all the elements mixed together in a "shapeless heap". Hyginus writes that "From Mist (Caligine) came Chaos. From Chaos and Mist, came Night (Nox), Day (Dies), Darkness (Erebus), and Ether (Aether)." Lastly, in Orphic tradition Chaos is considered the son of Chronos and Ananke.

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