Wilhelm Richard Wagner (pron.: //; German: [ˈʁiçaʁt ˈvaːɡnɐ]; 22 May 1813 – 13 February 1883) was a German composer, theatre director, polemicist, and conductor primarily known for his operas (or, as some of his later works were later known, "music dramas"). His compositions, particularly those of his later period, are notable for their complex textures, rich harmonies and orchestration, and the elaborate use of leitmotifs—musical phrases associated with individual characters, places, ideas or plot elements. His advances in musical language, such as extreme chromaticism and quickly shifting tonal centres, greatly influenced the development of classical music; his Tristan und Isolde is sometimes described as marking the start of modern music.
This list provides a guide to the most important opera composers, as determined by their presence on a majority of compiled lists of significant opera composers. (See the "Lists Consulted" section for full details.) The composers run from Jacopo Peri, who wrote the first ever opera in late 16th century Italy, to John Adams, one of the leading figures in the contemporary operatic world. The brief accompanying notes offer an explanation as to why each composer has been considered major. Also included is a section about major women opera composers, compiled from the same lists. For an introduction to operatic history, see opera. The organisation of the list is by birthdate.