In many cosmogonical- or creation-myths the state prior to creation, genesis or formation of the world (or universe). It should be noted that 'chaos' refers not only to a state of disorder, but also - originating from Greek khaos (Indo-european root: ghēu-; - means 'void, abyss, empty space', thus the two terms 'Chaos' and 'Void' are pretty much congruent.
Examples for such creation-myths can be found in Mesopotamian (e.g. the Babylonian Creation myth, aka Enuma Elish), Greco-Roman? (e.g. the Pelasgian or the Olympian Creation myth), Egyptian (cf. Nu or Num), but also Hebrew - and thus Judeo-Christian mythology (cf. Genesis 1).
See also Void