Dialogues des Carmélites (French pronunciation: [djalɔɡ de kaʁmelit], Dialogues of the Carmelites), FP 159, is an opera in three acts, divided into twelve scenes with linking orchestral interludes, with music and libretto by Francis Poulenc, completed in 1956. Poulenc wrote the libretto for his second opera after the work of the same name by Georges Bernanos, itself based on The Song at the Scaffold by Gertrud von Le Fort. This is a fictionalized version of the story of the Martyrs of Compiègne, Carmelite nuns who, in 1794 during the closing days of the Reign of Terror during the French Revolution, were guillotined in Paris for refusing to renounce their vocation.

The world première of the opera occurred (in Italian translation) on 26 January 1957 at La Scala in Milan. The première of the French-language version took place in Paris on 21 June 1957. The United States première, in English, followed in San Francisco in September 1957.

Bernanos had been hired in 1947 to write the dialogue for a film screenplay, through Raymond Léopold Bruckberger and the scenario writer Philippe Agostini, based on the novella Die Letzte am Schafott (literal translation, The Last on the Scaffold, or Song at the Scaffold, the published title of the English translation) by Gertrud von Le Fort. The novella is based on the story of the Martyrs of Compiègne at the monastery of Carmelite nuns in Compiègne, northern France, in the wake of the French Revolution, specifically in 1794 at the time of state seizure of the monastery's assets. It traces a fictional path from 1789 up to these events, when nuns of the Carmelite Order were guillotined.

The screenplay was judged unsatisfactory for a film. Bernanos died on 5 July 1948. Subsequently, his literary executor, Albert Béguin, found this manuscript. To assist Bernanos' surviving family, Béguin sought to have the work published, and requested permission from von Le Fort for publication. In January 1949, she agreed, and donated her portion of the royalties due to her, as creator of the original story, over to Bernanos' widow and children. However, von Le Fort requested that the Bernanos work be titled differently from her own novella. Béguin chose Dialogues des Carmélites as the title for the Bernanos work, which was published in 1949. A German translation of the work, Die begnadete Angst (The Blessed Fear), was published in 1951, and Zurich and Munich saw productions of Die begnadete Angst that year. The French stage premiere was by Jacques Hébertot in May 1952 at the Théâtre Hébertot.

The genesis of the opera was in 1953. Margarita Wallmann took her husband Guido Valcarenghi, president of Ricordi, which was Poulenc's publishing firm, to see the Bernanos play in Vienna. She had asked Poulenc to write an oratorio for her; through the commission from Ricordi, he developed the work as the opera. Wallman was the eventual producer of the La Scala première of Poulenc's opera, and she later supervised the 1983 revival at Covent Garden. About the same time, Valcarenghi had approached Poulenc with a commission for a ballet for La Scala in Milan.

Separately, Poulenc had seen the Bernanos play, but the suggestion from Ricordi finalised the impetus to adapt the subject as an opera. Poulenc began to adapt the Bernanos text in the spring and summer of 1953, and to compose the music in August 1953. In October 1953, Poulenc learned of a literary rights dispute between Béguin and the American writer Emmet Lavery, who had previously secured all rights to theatrical adaptations of von Le Fort's novel from her in April–May 1949. This was independent of the discussion, concluded in January 1949, between Béguin and von Le Fort. The two-year literary rights dispute between Béguin and Lavery reached arbitration by a jury from La Societé des Auteurs in Paris. On 20 July 1954, this jury ruled unanimously for Lavery, and ordered the Bernanos heirs to pay Lavery 100,000 FF for past contract infringements. In addition, the ruling required the Bernanos heirs to pay Lavery, with respect to all future productions of Dialogues des Carmélites, 15% of the royalties from English-language productions, and 10% from productions in all other languages.

Poulenc had curtailed work on his opera in March 1954, in light of his understanding of the Béguin-Lavery dispute. Following the July 1954 decision, separate negotiations occurred between Béguin and Lavery, via his agent Marie Schebeko, on rights and royalties to allow Poulenc to write his opera. The formal agreement was dated 30 March 1955, and acknowledged Bernanos, Lavery, von Le Fort, Bruckberger, and Agostini. The terms stipulated that the Poulenc opera was adapted from Bernanos 'with the authorization of Monsieur Emmet Lavery', with Lavery listed in the credits after Bernanos and before von Le Fort, without any contribution of material by Lavery to the libretto. Poulenc then resumed work on the opera, and completed it October 1955.

At this time, Poulenc had recommitted himself to spirituality and Roman Catholicism, although he was openly gay and the church officially opposed homosexuality. Opera critic Alan Rich believes that Poulenc's concern for the travails of post-World War II France, as it tried to reconcile issues related to the Holocaust, German occupation and the Resistance, was a subtext within the opera. Wallmann worked closely with Poulenc during the composition process and in evolving the structure, as well as later when she re-staged the production in other theatres. The libretto is unusually deep in its psychological study of the contrasting characters of Mother Marie de l'Incarnation and Blanche de la Force.