La fille du rgiment (The Daughter of the Regiment) is an opra comique in two acts by Gaetano Donizetti, set to a French libretto by Jules-Henri Vernoy de Saint-Georges and Jean-Franois Bayard. It was first performed on 11 February 1840 by the Paris Opra-Comique at the Salle de la Bourse.

The opera was written by Donizetti while he was living in Paris between 1838 and 1840 preparing a revised version of his then-unperformed Italian opera, Poliuto, as Les martyrs for the Paris Opra. Since Martyrs was delayed, the composer had time to write the music for La fille du rgiment, his first opera set to a French text, as well as to stage the French version of Lucia di Lammermoor as Lucie de Lammermoor.

La fille du rgiment quickly became a popular success partly because of the famous aria "Ah! mes amis, quel jour de fte!", which requires the tenor to sing no fewer than eight high Cs a frequently sung ninth is not written. La figlia del reggimento, a slightly different Italian-language version (in translation by Calisto Bassi), was adapted to the tastes of the Italian public.

Domenico Gaetano Maria Donizetti (29 November 1797 – 8 April 1848) was an Italian composer, best known for his almost 70 operas. Along with Gioachino Rossini and Vincenzo Bellini, he was a leading composer of the bel canto opera style during the first half of the nineteenth century and a probable influence on other composers such as Giuseppe Verdi. Donizetti was born in Bergamo in Lombardy. At an early age he was taken up by Simon Mayr who enrolled him with a full scholarship in a school which he had set up. There he received detailed musical training. Mayr was instrumental in obtaining a place for Donizetti at the Bologna Academy, where, at the age of 19, he wrote his first one-act opera, the comedy Il Pigmalione, which may never have been performed during his lifetime.An offer in 1822 from Domenico Barbaja, the impresario of the Teatro di San Carlo in Naples, which followed the composer's ninth opera, led to his move to Naples and his residency there until production of Caterina Cornaro in January 1844. In all, 51 of Donizetti's operas were presented in Naples. Before 1830, success came primarily with his comic operas, the serious ones failing to attract significant audiences. His first notable success came with an opera seria, Zoraida di Granata, which was presented in 1822 in Rome. In 1830, when Anna Bolena was first performed, Donizetti made a major impact on the Italian and international opera scene shifting the balance of success away from primarily comedic operas, although even after that date, his best-known works included comedies such as L'elisir d'amore (1832) and Don Pasquale (1843). Significant historical dramas did succeed; they included Lucia di Lammermoor (the first to have a libretto written by Salvadore Cammarano) given in Naples in 1835, and one of the most successful Neapolitan operas, Roberto Devereux in 1837. Up to that point, all of his operas had been set to Italian libretti.

Donizetti found himself increasingly chafing against the censorship limitations in Italy (and especially in Naples). From about 1836, he became interested in working in Paris, where he saw greater freedom to choose subject matter, in addition to receiving larger fees and greater prestige. From 1838, beginning with an offer from the Paris Opéra for two new works, he spent much of the following 10 years in that city, and set several operas to French texts as well as overseeing staging of his Italian works. The first opera was a French version of the then-unperformed Poliuto which, in April 1840, was revised to become Les martyrs. Two new operas were also given in Paris at that time. Throughout the 1840s Donizetti moved between Naples, Rome, Paris, and Vienna, continuing to compose and stage his own operas as well as those of other composers. From around 1843, severe illness began to limit his activities. By early 1846 he was obliged to be confined to an institution for the mentally ill and, by late 1847, friends had him moved back to Bergamo, where he died in April 1848 in a state of mental derangement due to neurosyphilis.