The Counter-Earth is a hypothesized by the pre-Socratic Greek philosopher Philolaus (c. 470 – c. 385 BC) to support his non-geocentric cosmology, in which all objects in the universe revolve around an unseen "Central Fire" (distinct from the Sun which also revolves around it). The Greek word Antichthon means "Counter-Earth."

The Counter-Earth is a hypothesized by the pre-Socratic Greek philosopher Philolaus (c. 470 – c. 385 BC) to support his non-geocentric cosmology, in which all objects in the universe revolve around an unseen "Central Fire" (distinct from the Sun which also revolves around it). The Greek word Antichthon means "Counter-Earth."