Les martyrs (French pronunciation: [le maʁtiʁ], The Martyrs) is a four-act grand opera by Gaetano Donizetti set to a French libretto by Eugène Scribe. The libretto was based on one written by Salvadore Cammarano for an original Italian version known as Poliuto, which was not performed until after the composer's death. Pierre Corneille's play Polyeucte written in 1641–42, the story of which reflected the life of the early Christian martyr Saint Polyeuctus, is the original source for both versions.

When Poliuto was banned by the King of Naples just before it was due to be performed in 1838, Donizetti became angry at this decision and, with a commission from the Paris Opéra due, he paid the penalty to the San Carlo for not producing an original work as a substitute, and left Naples for Paris arriving on 21 October.

As his first of two commissions for the Opéra, he proposed to revise Poliuto and, between 1839 and 1840, a French text was prepared by the noted French librettist and dramatist, Eugène Scribe, which conformed to the conventions of French grand opera but which incorporated 80% of the music from Poliuto. Revised to suit the taste of the Paris opera-going public and with the title changed to Les martyrs, the opera was presented on 10 April 1840.

When eventually given in Italy, Les martyrs was initially presented in a translation from the French version under several titles including I martiri. It took until 30 November 1848, months after the composer's death, in order for Poliuto to finally appear at the San Carlo in its original Italian three-act version, the one which is most frequently performed today.

It is regarded by one writer as Donizetti's "most personal opera" with the music being "some of the finest Donizetti was to compose".

Donizetti had been gradually considering further involvement with the Parisian stage after the tremendous success of his Lucia di Lammermoor at the Théâtre-Italien in December 1837. As Roger Parker and William Ashbrook note, "negotiations with Henri Duponchel, the director of the Opéra, took on a positive note for the first time" and "the road to Paris lay open for him", the first Italian to obtain a commission to write a real grand opera.

In addition, while Donizetti was in Venice for the premiere of Maria de Rudenz the following January, he had met and had been impressed with Adolphe Nourrit, who had been the principal tenor in Paris, having sung roles written for him by the major French composers such as Meyerbeer, Auber, Halévy, as well as Rossini (in William Tell) after that composer had moved to Paris in 1829. However, by the late 1830s, Nourrit's popularity in Paris was in decline, and he was in danger of being supplanted in the public's affections by rising star Gilbert Duprez who the composer had tried to interest in a Paris production of L'assedio di Calais (The Siege of Calais) in 1836, but which failed to gain attention outside Italy.

Donizetti returned to Naples on 24 February, where he began planning for the production of Poliuto but, at the same time, he had also hoped for a permanent supervisory appointment at the Collegio di San Pietro a Maiella there. However, the post went the composer, Saverio Mercadante. Therefore, on 25 May 1838, Donizetti responded to an invitation from the Paris Opéra to compose two new works, specifying that the contract would require a libretto from Scribe with specific performance dates and a rehearsal periods included. Now committed to produce his next opera for Naples, the composer wrote Poliuto "with more than half an eye to its potential for it being recast as a French grand opera".