Clytemnestra was the daughter of Tyndareus and Leda, the king and queen of Sparta. According to the myth, Zeus appeared to Leda in the form of a swan, seducing and impregnating her. Leda produced four offspring from two eggs: Castor and Polydeuces from one egg, and Helen and Clytemnestra from the other. Castor and Clytemnestra were fathered by Tyndareus whereas Polydeuces and Helen were fathered by Zeus.
Agamemnon and his brother Menelaus were in exile at the home of Tyndareus. In due time the brothers married Tyndareus' two daughters: Agamemnon marrying Clytemnestra and Menelaus marrying Helen. In a late variation, Euripides's Iphigenia at Aulis, Clytemnestra's first husband was Tantalus, King of Pisa (in the western Peloponnese), who was slain by Agamemnon. Agamemnon also murdered her infant son. He then forcibly made Clytemnestra his wife. In another version, her first husband was King of Lydia, which was known to the Greeks for its shrine of the labrys, the double-bladed ax that some say Clytemnestra used to kill Agamemnon.
With the help of troops from his new father-in-law, Agamemnon then took the throne of Mycenae from his uncle Thyestes. Agamemnon and Clytemnestra became rulers of Mycenae, and she bore three daughters: Iphigenia, Chrysothemis, and Electra; and finally a son: Orestes.
She is one of the main characters in Aeschylus's Oresteia, and is central to the plot of all three parts. She murders Agamemnon in the first play, and is murdered herself in the second. Her death then leads to the trial of Orestes by Apollo and the Furies in the final play.