Thespius was the king and namer of Thespiae, a city west of Thebes. His name is based on thespis, 'inspired', 'prophetic', 'divine' ( from theos, 'god' and epos, 'word', 'prophecy'), and indicates an actual or desirable oracular or prophetic gift.

The word 'Thespian', often used facetiously to mean 'actor' or 'actress', derives not from him but from a real person, Thespis, the sixth-century BC actor who was called the Father of Greek Tragedy.