Clément Philibert Léo Delibes (French: [klemɑ̃ filibɛʁ leo dəlib]; 21 February 1836 – 16 January 1891) was a French Romantic composer, best known for his ballets and operas. His works include the ballets Coppélia (1870) and Sylvia (1876) and the opera Lakmé (1883), which includes the well-known "Flower Duet".

Born into a musical family, Delibes enrolled at France's foremost music academy, the Conservatoire de Paris, when he was twelve, studying under several professors including Adolphe Adam. After composing light comic opérettes in the 1850s and 1860s, while also serving as a church organist, Delibes achieved public recognition for his music for the ballet La Source in 1866. His later ballets Coppélia and Sylvia were key works in the development of modern ballet, giving the music much greater importance than previously. He composed a small number of mélodies, some of which are still performed frequently.

Delibes had several attempts at writing more serious operas, and achieved a considerable critical and commercial success in 1883 with Lakmé. In his later years he joined the faculty of the Conservatoire, teaching composition. He died at his home in Paris at the age of 54. Coppélia and Sylvia remain core works in the international ballet repertoire, and Lakmé is revived from time to time in opera houses.

Delibes was born in Saint-Germain-du-Val, now part of La Flèche (Sarthe), on 21 February 1836; his father worked for the French postal service and his mother was a talented amateur musician, the daughter of an opera singer and niece of the organist Édouard Batiste. Delibes was the couple's only child. His father died in 1847 and the family moved to Paris, where soon after his twelfth birthday Delibes was admitted to the Paris Conservatoire. He studied first with Antoine-Jules Tariot (music theory), and then with Félix Le Couppey (piano), François Benoist (organ), François Bazin (harmony) and, at eighteen, Adolphe Adam (composition).

As a boy, Delibes had an unusually fine singing voice; he was a chorister at the church of La Madeleine and sang in the première of Meyerbeer's Le prophète at the Paris Opéra in 1849. While still a student Delibes became organist of St. Pierre de Chaillot [fr] and accompanist at the Théâtre Lyrique. At the latter he took part in the preparation of most of the operas in the theatre's repertoire, including classics such as The Marriage of Figaro and Fidelio and new works such as Louis Clapisson's La Fanchonnette, Victor Massé's La Reine Topaze and Gounod's Faust. His biographer Hugh Macdonald writes that although Delibes remained a church organist until 1871 (he held several posts, the last of them at the church of Saint Jean-Saint François from 1862), he was "clearly drawn more to the theatre [and] found his métier at Hervé's highly successful Folies-Nouvelles".

In 1856 Delibes' first stage work was premiered at the Folies-Nouvelles: Deux sous de charbon (Two sous-worth of coal), a one-act comic piece to a libretto by Jules Moinaux, described as an "asphyxie lyrique". Over the next fourteen years he produced more comic operas, at an average rate of about one a year. Many were written for the Bouffes-Parisiens, the theatre run by Jacques Offenbach, including Deux vieilles gardes ("Two Old Guards"), Delibes's second opera, which enjoyed enormous success, attributable in Macdonald's view to the composer's gift for "witty melody and lightness of touch".

In addition to composing, Delibes earned a living as a critic (briefly in 1858); inspector of school music; and accompanist and later chorus master at the Opéra (from 1862 or 1863).. His appointment at the Opéra led to a new career as a composer of ballet music. In 1866 he was commissioned to compose two acts of La Source, the other two being written by Ludwig Minkus. In the view of the musicologist and critic Adolphe Jullien, Delibes "displayed such a wealth of melody as a composer of ballet music" that Minkus was "completely eclipsed". Delibes was immediately invited to compose a waltz-divertissement called Le Pas de Fleurs to be introduced into the ballet of his former teacher Adam, Le Corsaire, for a revival in 1867. The piece was later incorporated into Delibes' music for La Source when it was revived.

In 1869 Delibes composed his last opérette, La Cour du roi Pétaud, for the Variétés. The following year he came to wider public notice with his score for the ballet Coppélia, first performed at the Opéra in May 1870. It was an immediate success, and has remained among the most popular works in the classical ballet repertoire. The following year he resigned from the musical staff of the Opéra and devoted himself wholly to composition. In that year he married Léontine Estelle Denain.