Grand Opéra is a style of opera largely characterized by many features on an excessive scale. Heroic and mythological subjects, large casts, vast orchestras, richly detailed sets, sumptuous costumes and spectacular scenic effects are all features of this genre, as well as continuous music (recitative instead of spoken dialogue), a four or five-act structure and the prevalence of ballets. Originating in mid-nineteenth century France, it fell into disfavor within several decades, as the expense of staging these mammoth works and the generally inferior quality of the music caused newer styles to gain in popularity. Nevertheless, grand opéra did not die out, many composers continued to write these works, and the style continued to be influential.

Paris at the turn of the nineteenth century drew in many composers, both French and foreign, and especially those of opera. This cosmopolitan combination of influences helped to form the style of grand opéra. Several Italians working during this period, in particular Luigi Cherubini, demonstrated that the use of recitative was suited for the powerful dramas that were being written. Others wrote works to glorify Napoleon, such as Gaspare Spontini, and these operas were composed on a suitably grand scale for the emperor. Added to the influence of a large Paris Opera House capable of staging a sizeable work and the long tradition of French ballet and stagecraft, the time was ripe for the combination of influences to bear fruit starting in the late 1820's.

The acknowledged superstar of this form is Giacomo Meyerbeer, who reached prominence in the Paris opera scene beginning with Robert le Diable in 1831. He followed this work with his masterpiece, Les Huguenots, in 1836. These and other works were huge box-office successes, and even inspired the young Richard Wagner to try his hand at grand opéra with his early work, Rienzi (1842).

Other important early grand opéras include Auber's La Muette de Portici (1828), Rossini's Guillaume Tell (his final opera; 1829), and Halévy 's La Juive (1835). These operas, while not generally seen as outright failures, were not the most popular examples in their day, even though they are now viewed as being among the most influential and among the higher quality grand opéras. Other notable examples are the popular Faust (1859) by Charles Gounod and Les Troyens by Hector Berlioz (composed from 1856-1858, later revised, and not given a full performance until a century after Berlioz had died, although portions had been staged before).

Eventually, there was a backlash against the excesses of the style, and composers generally favored writing other types of opera, although many of these continued to be of a serious nature and incorporated some elements from grand opéra. Many serious operas written later are also called grand opéra even if they lack some elements of the form. Perhaps the most popular example after the general decline of the style in France is Verdi's Aida, first performed in 1871.

Today only a handful of these works survive, as their sheer length and the expense of staging them can still be prohibitive, even for the largest opera houses.