The astral body is a subtle body posited by many philosophers, intermediate between the intelligent soul and the mental body, composed of a subtle material. In many recensions the concept ultimately derives from the philosophy of Plato though the same or similar ideas have existed all over the world well before Plato's time: it is related to an astral plane, which consists of the planetary heavens of astrology. The term was adopted by nineteenth-century Theosophists and neo-Rosicrucians.

In esoteric cosmology, a plane is conceived as a subtle state, level, or region of reality, each plane corresponding to some type, kind, or category of being.