Chamber opera is a designation for operas written to be performed with a chamber ensemble rather than a full orchestra.
The term and form were invented by Benjamin Britten in the 1940s, when the English Opera Group needed works that could easily be taken on tour and performed in a variety of small performance spaces. The Rape of Lucretia was the first example of the genre, and Britten followed it with Albert Herring, The Turn of the Screw and Curlew River. Other composers, including Hans Werner Henze, Harrison Birtwistle, Thomas Adès, George Benjamin and Philip Glass, have since adopted the term for their own works.
Instrumentation for a chamber opera will vary: Britten scored The Rape of Lucretia for eight singers with single strings and wind with piano, harp and percussion. Matthew King's The Snow Queen has three singers in multiple roles, with an ensemble of seven players while Judith Weir's King Harald's Saga is for a single soprano voice.
The term chamber opera is also sometimes used to describe smaller Baroque operatic works such as Pergolesi's La serva padrona and Charpentier's Les Arts florissants, which also use small instrumental and vocal ensembles.