- 1733 
- English translation The magus Zoroastro studies the stars, divining in their patterns that the errant Carolingian knight Orlando will not always be a foe to valour and duty.
Orlando appears, torn between his ordained role as a warring knight and his love for the princess Angelica, Queen of Cathay.
Zoroastro challenges Orlando to return to his true path; after showing Orlando disturbing images of his downfall and spiritual decay, he exhorts him to abandon Venus and follow Mars.
Orlando hesitates for a moment… before resolving to have both.
Dorinda, a shepherdess, contemplates the beauty of nature, and yet feels the pangs of love stirring within her. She has been giving shelter to Angelica and the Moorish soldier Medoro, whom Angelica found near death and brought to the shepherdess to help nurture him back to health.
Orlando appears, rescuing the hapless princess Isabella from her captors. Dorinda, mistakenly believing Orlando to be in love with Isabella, comments that she may well have something in common with him – but is it really love that she is feeling?
Angelica appears, and recalls the moment she saw the injured Medoro for the first time. She has fallen desperately in love with him, and the pair are now lovers.
When Angelica has left, Dorinda finds Medoro and expresses her fears that he may be more than just a friend to Angelica. Medoro explains to her that he owes Angelica his life and will soon leave with her; rather disingenuously he reassures Dorinda that he will never forget her.
Dorinda, knowing deep down that he is just flattering her, nevertheless decides to cheer herself up with his false words.
Zoroastro warns Angelica to fear the wrath of Orlando, should he ever discover that she loves someone else. Seeing Orlando approaching, he conceals himself, resolving to protect Angelica and Medoro. Angelica reveals herself to Orlando, seeking to find a way out of her situation; hoping that he may be in love with Isabella, she feigns jealousy to discover whether this may actually be the case or not. Orlando vigorously denies any love for Isabella, declaring Angelica to be his true love. Angelica, hoist by her own petard, orders Orlando never to help Isabella again, or Angelica will disappear forever from his life.
Orlando dejectedly agrees to this, and vows to honour Angelica with countless trophies of war.
Medoro rushes in as Orlando leaves, and demands to know whom Angelica was with. Angelica explains, and knowing that he will never be a match for Orlando’s strength, tells him to save himself for love. She resolves to leave with Medoro and return to he Eastern kingdom to escape Orlando’s wrath. Dorinda enters and sees them in a passionate embrace. The couple can hide their love no longer, and reassure the dejected Dorinda that she too will one day find love. Angelica gives Dorinda a jewel as a token of her thanks for her hospitality.
Act 2
The dejected Dorinda empathises with a nightingale’s sad melody.
Orlando appears and demands to know why Dorinda has told Angelica that he was in love with Isabella. Dorinda denies this, and goes on to explain her sadness at Angelica and Medoro’s love for each other. When Orlando demands proof, she shows him the jewel that Orlando has given her. Dorinda pines that she now sees Medoro in every flower and in every tree.
Orlando, devastated at this news, vows revenge on Angelica. Born under a spell of magic invulnerability, he implores heaven to kill him too.
Zoroastro urges Angelica and Medoro to flee, promising to protect them on their journey. This nevertheless points to the moral that love can lead to ruin and sadness if the light of reason is not there to act as a guide.
Angelica and Medoro are sad at having to leave the verdant caves and limpid streams where their love first blossomed. Medoro carves their names into the trees to preserve their memory there forever.
Angelica still feels guilty at having lied to Orlando; she tells herself however that he will understand, as he too has been pierced by love’s arrow and will thus sympathise with her predicament.
Angelica too bids farewell to the plants and streams that had brought her such pleasure.
Orlando rushes in on Angelica, vowing to kill her. Angelica pleads in vain for Medoro to rescue her. She tries to escape, and is rescued by Zoroastro’s genies who sweep down from heaven on a cloud and whisk her away.
Orlando, enraged, curses heaven. Madness sets upon him – all the fury he was to expend on Angelica now turns inward and he imagines himself a shadow, entering Hades. Hallucinating, he sees Medoro in the arms of Proserpina, the wife of Pluto, and runs to kill him, but suddenly notices that Proderpina is crying, and begs her to stop. Anger boils up inside Orlando once more, but before he is able to do himself any harm, Zoroastro appears and carries him to safety.
Act 3
Medoro, separated from Angelica in the confusion, returns to Dorinda’s hut and shamefacedly tells her that he would give his heart to her if he could, but that it is no longer his to give.
Dorinda comments on the madness of love and the folly which it creates.
Zoroastro appears and reaffirms the moral that reason is easily destroyed by love. He transforms the setting from a peaceful forest into a dark cave, setting the scene for Orlando’s eventual return to sanity.
Angelica returns, and finds Dorinda crying. When asked why, Dorinda can barely tell her – the raging Orlando has destroyed her cottage, apparently burying Medoro in the rubble. Orlando appears and confronts Angelica, who devastated, begs him to kill her.
Orlando violently hurls Angelica into the cave, which is suddenly transformed by Zoroastro into the Temple of Mars.
Orlando triumphantly declares himself to have ridden the earth of every monster and every evil spirit. Overcome by tiredness, he imagines himself drinking the opiate waters of the river of Lethe, and falls asleep.
Zoroastro proclaims that the hour has come for Orlando’s sanity to be returned to him; a bird descends from the moon with a phial, and Zoroastro sprinkles the contents over Orlando.
The knight awakes, and Dorinda regales him with the horrific deeds he committed while insane- killing Angelica and Medoro. Overcome with grief, Orlando resolves to kill himself.
Angelica and Medoro appear, to Orlando’s joy, both having been saved by Zoroastro. Angelica forgives Orlando for his actions, and Zoroastro begs him on behalf of the lovers for his blessing of their relationship. Orlando willingly concedes, and declares himself forever the servant of valour and war. Dorinda invites everyone back to her cottage to celebrate. All join in praise of the equal merits of love and valour.
| Orlando | Countertenor | M-H | A knight in Charlemagne's army |
| Angelica | Soprano | F-H | Queen of Cathay |
| Medoro | Alto | M-VH | An African prince |
| Dorinda | Soprano | F-H | A shepherdess |
| Zoroastro | Bass | M-VL | A magician |