Andromaca (Andromache): Princess of Troy, widow of the hero Hector, who was heir to the Trojan throne. Mother of Astianatte.

Pirro (Pyrrhus): King of Epirus, an ally of Greece in the Trojan War. Son of the great warrior Achilles, who killed Hector.

Ermione (Hermione): Princess of Sparta, daughter of Helen of Troy, engaged to Pirro.

Oreste (Orestes): Prince of Mycenae; son of Agamemnon, who led the Greeks during the Trojan War. Ermione's cousin.

Pilade (Pylades): Oreste's friend.

Clearte: Pirro's attendant.

Astianatte (Astyanax): A child, son of Andromaca and Hector (non-singing role).

The action takes place in the aftermath of the fall of Troy.

ACT I

Pirro, King of Epirus, confesses that he is desperately in love with his captive, the Trojan princess Andromaca. But the bad blood between them runs deeper than mere wartime enmity; She will not forget that it was Pirro's father, Achilles, who slew her husband, the Trojan hero Hector. In spite of Pirro's pleas and threats, Andromaca refuses to marry him, even though he promises support and safety for her young son Astianatte.

Pirro's attendant, Clearte, reports that the prince Oreste is arriving with an embassy from the Greeks. Their mission is unknown, but there is concern that in his infactuation with Andromaca, Pirro is delaying his politically-arranged marriage to Oreste's cousin, the Spartan princess Ermione.

Oreste arrives and delivers an ultimatum: Astianatte, being Hector's offspring, is a threat to the Greeks as long as he remains alive. Either Pirro kills him, or the marriage with Ermione is off. Pirro bridles at the Greeks' arrogance and says he will not be pressured. He will renounce Ermione instead. Oreste is startled. He has long loved Ermione, and she once loved him in return. Now he hopes revive, and his friend Pilade encourages him.

But Ermione's attachment to her honor far outweighs any affection for Oreste. For Pirro she has no feelings at all, yet she is absolutely unwilling to tolerate the humiliation of being rejected in favor of the mere Trojan slave Andromaca. Playing on Oreste's love, she demands that he avenge the slight she has suffered.