Irony is a particular rhetorical device employed when a speaker wishes to convey an opposite meaning. There are three separate types of irony: verbal, dramatic, and situational. Dramatic irony is such that the audience of a particular piece of drama is aware of information that the characters are not. The single most famous example of dramatic irony derives from the ancient Greek play Oedipus the King, by Sophocles.
In Oedipus the King, Oedipus vows to root out the killer of the former king. The audience, however, is aware that it is Oedipus himself who is this killer. Yet none of the main characters—Oedipus, Jocasta, or Creon—are aware of this reality. Dramatic irony has been used by numerous other playwrights since. William Shakespeare frequently used dramatic irony in his tragedies. Notable Shakespearean plays that use dramatic irony include Romeo & Juliet and Othello.
The use of dramatic irony within a tragic play, such as Oedipus the King is often referred to as tragic irony. The audience is aware of the ending of the story. Oedipus, we know, will blind himself and fall from his lofty position in society. The dramatic irony results in watching the downfall play out, especially as the words of the character, in this case Oedipus, come back to haunt him. A modern example of dramatic irony can be found in the film The Truman Show, in which everyone but Truman knows that his entire life is a television show.