Daemon is the Latin word for the Ancient Greek daimon (δαίμων: "god", "godlike", "power", "fate"), which originally referred to a lesser deity or guiding spirit; the daemons of ancient Greek religion and mythology and of later Hellenistic religion and philosophy.

A tradition of Greek thought which found agreement in the mind of Plato, was of a daimon which existed within a person from their birth, and that each individual was obtained by a singular daimon prior to their birth.

Daemons scarcely figure in Greek mythology or Greek art: they are felt, but their unseen presence can only be presume.