Chaos was, according to Greek mythology, the origin of everything, and the first thing that ever existed. It was the primordial void, the source out of which everything was created, including the universe and the gods. The first primordial deities that emerged out of Chaos were Gaea (earth), Tartarus (underworld) and Eros (love), while later Erebus (darkness) and Nyx (night) also popped out. According to Hesiod, Chaos was also a place, much like Tartarus and the Heavens later, beyond which the Titans lived.
Chaos Is also called Chaos, Haos, Khaos, Arche.