"scenical representations, which Thespis is first reported to have invented"
Creative Commons AttributionThespis - Credit: sailko

Ancient Greek sources record Thespis of Icaria as the first person ever to appear on stage as an actor playing a character, in 6BC.  Aristotle described Thespis as a singer of dithyrambs, songs about stories from mythology.  He is credited with introducing a new style in which one singer or actor performed the words of individual characters, distinguishing between them with the aid of different masks.  Thespis also invented theatrical touring, touring cities with his costumes, masks and other props.

Actors are commonly referred to as thespians, in recognition of this trail-blazing entertainer.