Corax, along with Tisias, was one of the founders of Greek rhetoric. It has sometimes been asserted that they are merely legendary personages. Other scholars contend that Corax and Tisias were the same person, described in one fragment as "Tisias, the Crow" (Corax is Greek for "crow.")

Corax is said to have lived in Sicily in the fifth century BC. During his time, Thrasybulus, the tyrant of Syracuse, was overthrown and a democracy formed. Under the despot, the land and property of many common citizens had been seized; these people flooded the courts in an attempt to recover their property.

Corax devised an art of rhetoric to permit ordinary men to make their cases in the courts. His chief contribution was in helping structure judicial speeches into various parts: proem, narration, statement of arguments, refutation of opposing arguments, and summary. This structure is the basis for all later rhetorical theory.

His pupil, Tisias, is said to have developed legal rhetoric further, and he may have been the teacher of Isocrates.

All we know of the work of Corax is from references made by later writers, such as Plato, Aristotle, and Cicero.