Clitemnestra or Clitenestra (Greek: Κλυταιμνήστρα) was, in Greek mythology, the wife of Agamemnon, leader of the Greek armies at Troy. The beautiful queen was the non-identical twin sister of Helen, of Castor and Pollux, and daughter of Leda with Tyndareus.
Married in first marriage to Tantalus II, son of Tiestes, she had her husband murdered by Agamemnon who desired her. She married him, but her brothers, revolted by the crime, went against her brother-in-law and declared war on him.
Tyndareus, however, who had advised his son-in-law to kidnap his own daughter, gave Agamemnon shelter in his court and, with great difficulty, dissuaded his sons from a rematch, convincing them to conciliate with his brother-in-law.
Clytemnestra, revolted by the sacrifice of her daughter Iphigenia to Artemis by her own father Agamemnon, took revenge on her husband by teaming up with his cousin, Aegistus, to murder him and then rule over the people of Mycenae. After this, she rejected her other two children, Electra and Orestes.
Electra continued to live in the castle, but when she discovered that Aegistus was plotting her brother's death, she took him to live at the court of her uncle, King Strophius, and lived as her own mother's slave.
Later, when Orestes becomes an adult, he teams up with his sister, and avenges their father's murder.
Repentant, Clytemnestra apologizes for having abandoned and rejected her children, talks about how she had never stopped thinking about Orestes any time, that she treated Electra as a slave for fear that Aegistus would do something to her daughter, and even says that she had always loved them, showing the breasts that had nursed them. No effect.
Orestes and Electra killed Clytemnestra and Aegistus, in the plot told by Aeschylus, named Oresteia (also called Oresteia, Orestia or Orestiada). Orestes and Pilad enter, the palace and put the project into execution.
Orestes hesitates for a moment when he sees his mother; but the memory of his slain father overwhelms him, and Clytemnestra is struck down at the same time as Aegistus. This scene appears on some ancient monuments, in bas-reliefs and engraved stones.
In ancient representations, Egystus is always struck by Pillad and Clytemnestra by Orestes. In an ancient bas-relief from the Pio-Clementino museum, Electra participates in the scene.