Deidamia (HWV 42) is an opera in three acts composed by George Frideric Handel to an Italian libretto by Paolo Antonio Rolli.
The ambassadors from Agamemnon arrive on Skyros: Ulysses, disguised under the name of Antilochus, Phoenix and Nestor (a silent role).
Pyrrha – Achilles in disguise – returns flushed with his exertions and rebukes the women for sitting idly indoors.
Deidamia's confidante, the princess Nerea, brings news of the strangers arrived from mainland Greece in search of Achilles.
Ulysses has been watching 'Pyrrha' and now joins Phoenix: the strange girl's strength and skill in hunting have convinced him that 'she' is in fact Achilles in disguise.
Finding an opportunity to draw 'Pyrrha' aside Ulysses begins a feigned declaration of love; Achilles is flattered and amused, and more so when he notices that Deidamia is in hearing.
Phoenix tries to persuade Nerea that he is in earnest: as a Greek woman herself she should be proud, not jealous, that he is soon to leave for the Trojan war.
As Deidamia frantically urges Achilles to show a girlish interest in them, he instinctively reaches for a helmet, shield and sword cunningly placed amongst the trinkets.
Achilles, now at last dressed as a man, comes to Deidamia and proposes that they marry immediately, but her anger and distress at his imminent departure lead them into a quarrel.
Ulysses pacifies them by revealing his own identity: he too has famously left his much-loved wife Penelope to go to war, to the greater glory of them both; he predicts that Achilles and Deidamia will achieve similar fame.