• Wolfgang Amadeus Mozart. Dramma per musica in three acts. 1781.
• Libretto by Giovanni Battista Varesco, after Antoine Danchet's libretto of 1712 for André Campra.
• First performance at the Residenztheater, Munich, on 29th January 1781.

Ilia, a Trojan prisoner in Crete, is in love with Idamantes, son of Idomeneus, who, it seems, may have perished with the Greek fleet. Ilia imagines that the Greek princess Electra may fare better with Idamantes, who enters, bringing news of the sighting of the Greek fleet and the decision to release the Trojan prisoners, while he remains captive to the charms of Ilia. Electra objects to this act of clemency, and Arbaces enters with the news that the fleet has sunk. Idomeneus, however, has survived, thanks to the vow he has made to Neptune to sacrifice the first living being he meets on his return. Idamantes approaches him, neither of them recognising the other. When Idomeneus learns that the other is his son, he rushes away. In the second act Idomeneus confides in Arbaces, who suggests that Idamantes should go away, escorting Electra back to Argos, until some other solution may be found. As they are about to board ship, a storm arises and a sea- monster emerges. Idomeneus admits the vow he has made, but does not give the name of his son. In the third act Ilia and Idamantes are together in the palace gardens, joined there by Idomeneus and Electra, all expressing their conflicting feelings. The sea-monster meanwhile has been causing devastation and Idomeneus admits to the High Priest of Neptune that the sacrificial victim should be his son Idamantes. He, however, has killed the monster and now offers himself as a victim. Ilia tries to take his place, but the voice of Neptune bids Idomeneus abdicate in favour of his son, who should marry Ilia, a command that allows Electra a final expression of jealousy and anger. Idomeneus is grateful for the rest that retirement will bring.

The overture to Idomeneo, re di Creta (Idomeneus, King of Crete) is closely reflected in the opera itself, a fine reworking of a traditional opera seria subject. The Munich orchestra, formed principally from players who had followed the Elector from Mannheim to his new capital, included a larger string section and a pair of clarinets, an important instrument that was only now finding its proper place in the orchestra. There is ballet music and a chaconne for chorus to end the first act. Ilia, in an additional aria for 1786, opens the second act by seeking reassurance from Idamantes, whose Non temer, amato bene (Do not fear, well beloved) later served as a concert aria. Her third act Zeffiretti lusinghieri (Pleasant breezes) asks the winds to take her messages of love to Idamantes. Electra has a very notable and dramatic angry aria in her D'Oreste, d'Ajace (Of Orestes, of Ajax), a contrast with the resigned Torna la pace (Peace returns) of Idomeneus, which follows. The second of the arias of Idomeneus, Fuor del mar (Out of the sea) celebrates his survival after ship- wreck in floridly ornamented music that also exists in a simplified version. His first aria, Vedrommi intorno (I shall see around me), had expressed his fears at the rashness of his vow to Neptune, whose voice, from his stone statue, prefigures that of the Commendatore's statue in Don Giovanni.