An opera house is a theatre building used for opera performances that consists of a stage, an orchestra pit, audience seating, and backstage facilities for costumes and set building. While some venues are constructed specifically for operas, other opera houses are part of larger performing arts centers.

The first public opera house was the Teatro San Cassiano in Venice, Italy, which opened in 1637. Italy, where opera has been popular through the centuries among ordinary people as well as wealthy patrons, still has a large number of opera houses. When Henry Purcell was composing, there was no opera house in London. The first opera house in Germany was built in Hamburg in 1678. Early U.S. opera houses served a variety of functions in towns and cities, hosting community dances, fairs, plays, and vaudeville shows as well as operas and other musical events.

In the 17th and 18th centuries, opera houses were often financed by rulers, nobles, and wealthy people who used patronage of the arts to endorse their political ambitions and social positions or prestige. With the rise of bourgeois and capitalist social forms in the 19th century, European culture moved away from its patronage system to a publicly supported system. In the 2000s, most opera and theaters raise funds from a combination of government and institutional grants, ticket sales and, to a smaller extent, private donations.

Grand opera is a genre of 19th-century opera generally in four or five acts, characterised by large-scale casts and orchestras, and (in their original productions) lavish and spectacular design and stage effects, normally with plots based on or around dramatic historic events. The term is particularly applied (sometimes specifically using in its French language equivalent grand opéra, pronounced: [ɡʁɑ̃t‿ɔpeˈʁa]) to certain productions of the Paris Opéra from the late 1820s to around 1850; 'grand opéra' has sometimes been used to denote the Paris Opéra itself.

The term 'grand opera' is also used in a broader application in respect of contemporary or later works of similar monumental proportions from France, Germany, Italy and other countries.

It may also be used colloquially in an imprecise sense to refer to 'serious opera without spoken dialogue'.

Paris at the turn of the 19th century drew in many composers, both French and foreign, and especially those of opera. Several Italians working during this period including Luigi Cherubini demonstrated that the use of recitative was suited for the powerful dramas that were being written. Others, such as Gaspare Spontini, wrote works to glorify Napoleon. These operas were composed on a suitably grand scale for the Emperor. Other factors which led to Parisian supremacy at operatic spectacle was the ability of the large Paris Opéra to stage sizeable works and recruit leading stage-painters, designers and technicians, and the long tradition of French ballet and stagecraft. The first theatre performance ever lit by gas, for example, was Aladin ou La lampe merveilleuse at the Opéra in 1823; and the theatre had on its staff the innovative designers Duponchel, Cicéri and Daguerre.