Agamemnon, son of Atreus and King of Argos and Mycenae; Commander-in-Chief of the Greek armies in the War against Troy + 

Clytemnestra, daughter of Tyndareus, sister of Helen; wife to Agamemnon + 

Aigisthos, son of Thyestes, cousin and blood-enemy to Agamemnon, lover to Clytemnestra + 

Cassandra, daughter of Priam, King of Troy, a prophetess; now slave to Agamemnon + 

A Watchman + 

A Herald + 

Chorus of Argive Elders, faithful to Agamemnon + 