Orestes
The defendant. He killed his mother on Apollo's command to avenge his father. He's haunted by the Furies and largely passive during the trial, relying on divine advocates to make his case. His fate drives the plot, but his character is less important than what his case represents.
The Furies (Erinyes)
Ancient goddesses of vengeance who pursue anyone who kills a blood relative. They are the antagonists in terms of plot, but their argument is legally and morally serious. By the end they become the Eumenides, honored protectors of Athens, which is the play's central transformation.
Athena
The goddess of wisdom and the founder of the Athenian court. She refuses to judge alone, invents the jury, casts the deciding vote, and then negotiates with the Furies after the verdict. She's the play's most active and consequential figure.
Apollo
Orestes's divine advocate. He ordered the killing of Clytemnestra and defends that command at trial. His argument about parenthood is controversial and doesn't fully convince the jury. He represents the Olympian order but also its limits.
The Ghost of Clytemnestra
Appears briefly to shame the sleeping Furies into action. She has no legal standing in the trial, but her presence reminds the audience that a real woman was killed and that the Furies' anger has a legitimate source.