Orestes (in classical Greek: Ὀρέστης), in Greek mythology, was the son of King Agamemnon of Mycenae and Queen Clytemnestra, and the younger brother of Iphigenia.
Clitemnestra and her lover, Aegistus, killed Agamemnon as he was returning from the Trojan War. The only one who could avenge the crime, Orestes went to Phocida because he suspected that his mother's lover intended to kill him as well. There he grew up safely at the court of Strophius and befriended his cousin's son, Pilades.
When he became an adult, in obedience to Apollo's orders, Orestes killed his mother and Aegistus. Pursued by the Erynias, he took refuge in the sanctuary of Apollo in Delphi. Judged for his crime in Athens, the goddess Athena's vote broke the tie in his favor.
Again by order of Apollo, Orestes left for Tahurida to steal the statue of Artemis and return it to the city of Athens. Arrested with Pillades, he was condemned to be sacrificed to the goddess, but his sister Iphigenia, a priestess of Artemis, recognized him and fled with him and Pillades, taking the statue of the goddess.
Saved, he inherited Agamemnon's kingdom, to which he annexed Sparta and Epirus, after his marriage to Hermione, daughter of Menelaus and Helen. He died at the age of ninety, bitten by a serpent.