Electra or Elektra is a Greek tragic play by Sophocles. We do not know its date, but various stylistic similarities with the Philoctetes (409 BC) and the Oedipus at Colonus (401 BC) lead scholars to suppose that it was written towards the end of Sophocles' career.
When King Agamemnon returned from the Trojan War with his new concubine, Cassandra, his wife Clytemnestra (who has taken Agamemnon's cousin Aegisthus as a lover) kills them. Clytemnestra believes the murder was justified, since Agamemnon had sacrificed their daughter Iphigeneia. Electra, daughter of Agamemnon and Clytemnestra, rescued her infant brother Orestes from her mother by sending him to Strophius of Phocis. The play begins years later when Orestes has returned as a grown man with a plot for revenge.
Orestes arrives with his friend Pylades, son of Strophius, and a paedagogus (an old attendant of Orestes, who took him from Electra to Strophius). Their plan is to have the paedagogus announce that Orestes has died in a chariot accident, and that two men (really Orestes and Pylades) are arriving shortly to deliver an urn with his remains.
Electra laments over her father, first on her own, then (in lyrics) with the newly-arrived chorus. She bitterly argues first with her sister Chrysothemis over her accommodation with her father's killers, and then with her mother over her father's murder. Her only hope is that one day her brother will return to avenge him. When the messenger arrives with news of the death of Orestes, Clytemnestra is relieved to hear it. Electra however is devastated. Chrysothemis then enters: she has seen some offerings at the tomb of Agamemnon and (correctly) concludes that Orestes has returned. Electra dismisses her arguments, sure that Orestes is now dead. She suddenly turns to her sister with a proposal to kill Aegisthus, but Chrysothemis refuses to help, pointing out the impracticability of the plan.
After a choral ode Orestes arrives, carrying the urn supposedly containing his ashes. He does not recognise Electra, nor she him. He gives her the urn and she delivers a moving lament over it, unaware that her brother is in fact standing alive next to her. Now realizing the truth, Orestes reveals his identity to his emotional sister. She is overjoyed that he is alive, but in their excitement they nearly blow his cover, and the paedagogus comes out from the palace to urge them on. Orestes and Pylades enter the house and slay his mother Clytemnestra. As Aegisthus returns home, they quickly put her corpse under a sheet and present it to him as the body of Orestes. He lifts the veil to discover who it really is, and Orestes then reveals himself. They escort Aegisthus off set to be killed at the hearth, the same location Agamemnon was slain. The play ends here, before the death of Aegisthus is announced.
The story of Orestes' revenge was told at the end of the lost epic Nostoi, and the events are also brought up in the Odyssey. It was a popular subject in Greek tragedies, and there are surviving versions from all three of the great Athenian tragedians: Aeschylus, Sophocles, and Euripides. The first and largest is the Oresteia Trilogy by Aeschylus (458 BC). Euripides wrote an Electra play. He tells a very different version of this same basic story as Sophocles despite them being written in proximity and time.