Clytemnestra is the daughter of Tyndareus, the sister of Helen, and the wife of Agamemnon. The actor who portrays her usually does not play any other role in the play; in the original production, she may have even been played by Aeschylus himself.

Clytemnestra first comes onstage in the first episode, and she plays a role in all the subsequent scenes. She is the prime mover of the action of the play, though it is only in the final scene that the full extent of her role becomes apparent; it becomes clear that all of her actions built toward achieving the murder of her husband. The murderess is characterized throughout the play as masculine. The watchman, for instance, refers to her “male strength of heart” (11). The chorus likens her to “a prudent man” (351), and Agamemnon questions whether the way she addresses him is ”womanlike” (940). Clytemnestra herself warns the chorus not to think of her as “a woman and vain” (1401). Indeed, her actions—addressing the chorus and the city publicly, taking control of the city, and violently murdering her husband—display the boldness and courage that the ancient Greeks associated with men, rather than with women.

Clytemnestra is also a very calculating figure.