XXVIII/12) is a 1784 opera (dramma eroico) in three acts by Austrian composer Joseph Haydn, set to an Italian-language libretto taken from Antonio Tozzi's 1775 opera Rinaldo, as amended by Nunziato Porta [it], and ultimately based on the story of Armida and Rinaldo in Torquato Tasso's poem Gerusalemme liberata (Jerusalem Delivered).

Rinaldo also incorporated elements from Niccolò Jommelli's opera Armida abbandonata, first performed in 1770 at the Teatro San Carlo in Naples with a libretto by Francesco Saverio De Rogati [it], who had adapted it from his earlier drama based on Tasso's Gerusalemme liberata.

[3][4][5][6] A recitative in Act 3, relating Rinaldo's visit to the enchanted forest of Armida, was set by several other composers before it was included in Haydn's opera.

[7] Rinaldo also incorporated material from Giovanni Bertati's libretto for Johann Gottlieb Naumann's 1773 opera Armida that was also used in Haydn's version.

[8] Armida then disappeared from the general operatic repertoire; it was revived in 1968 in a concert rendition in Cologne, and later a production in Bern.

Sarah Reese sang the title role; the director Peter Sellars set the production during the Vietnam War.

To prevent the capture of Jerusalem by the knights of the First Crusade, The Prince of Darkness has sent the enchantress Armida into the world to seduce the Christian heroes and turn them from their duty.

The heathen sorceress Armida seems to have triumphed over the crusaders, but fears that her conquest is not complete without gaining the love of the Christian knight Rinaldo.

Idreno sends Zelmira, the daughter of the sultan of Egypt, to ensnare the Christians but on encountering Clotarco she falls in love with him and offers to lead him to safety.

Rinaldo, knowing that the tree holds the secret of Armida's powers, enters the wood intending to cut it down.