In Greek mythology, Orestes was the son of Agamemnon and Clytemnestra and the brother of Electra and Iphigenia. Known by the patronymic Agamemnonides, he avenges his father's murder by slaying Aegisthus and his own mother, then suffers madness and pursuit by the Erinyes until purified or acquitted — most famously in Aeschylus's Oresteia. His story of revenge, pollution, and trial is among the most retold cycles of Greek tragedy.
Adapted from Wikipedia, "Orestes" · CC BY-SA 4.0
I.Exile and vengeance
Orestes belongs to the doomed house of Atreus. He is absent when Agamemnon returns from Troy with Cassandra and is murdered by Aegisthus and Clytemnestra. In Homeric outline he later returns from Athens and kills both. Pindar and later authors say a nurse or Electra saved him as a child and took him to Strophius at Phanote on Mount Parnassus, where he was reared with his cousin Pylades.
In his twentieth year Apollo's oracle (and Electra's urging) send him home. With Pylades he kills Aegisthus and Clytemnestra — the core act that Greek drama then subjects to moral and legal scrutiny.
II.Madness, the Erinyes, and purification
In Aeschylus's Eumenides the Erinyes pursue Orestes for matricide. He takes refuge at Delphi, then at Athens; Athena founds the Areopagus court, Apollo defends him, and a tied vote (with Athena's ballot) acquits him, converting the Furies into the kindly Eumenides. Other traditions purify him elsewhere — among the Taurians in Euripides's Iphigenia among the Taurians, where he and Pylades nearly die before recognizing Iphigenia, or at sites Pausanias links to the Maniae.
Euripides's Electra, Orestes, Andromache, and Iphigenia plays, and Sophocles's Electra, vary the tone of the revenge and the aftermath. Orestes often marries Hermione and gives Electra to Pylades; he recovers Mycenae/Argos and figures in later Argive and Spartan legend.
III.Cult and later tradition
Herodotus recounts that the Spartans, advised by Delphi, recovered Orestes's bones from Tegea as a talisman of hegemony. Pausanias describes cult geography tied to his madness and cure in Arcadia. Roman and later authors treat him as an emblem of filial duty, pollution, and hard-won justice.
The Oresteia remains the foundational dramatic treatment; modern adaptations continue to use Orestes for themes of inherited violence, legal order, and the psychology of revenge.