Protagonist - the leading character of a drama, novel, etc. This is not always the hero, but is always the principal and central character whose rival is the antagonist.
The term is from the Greek protagonistes, meaning “first actor in a drama.”
The Greek tragic poet was restricted to three actors: protagonist, deuteragonist, and tritagonist, or first, second, and third actor. In contests between actors, only the protagonists were considered.
Originally, Greek drama probably consisted of only a Chorus and the leader of the Chorus. Thespis (Sixth Century B.C.) added the first actor, Aeschylus the second, and Sophocles the third.
Some famous protagonists are Hester Prynne from Hawthorne’s The Scarlet Letter, Atticus Finch from Lee’s To Kill a Mockingbird, and the title character of Hamlet.