Opera, as a musical and theatrical genre, began to emerge during the early part of Monteverdi's career, initially as a form of courtly entertainment. With other composers, he played a leading role in its development as the main form of public musical theatre. Subsequently the composers Handel and Gluck developed the court opera in the 17th and 18th Century throughout Europe. In addition, the reform of opera by Willibald Gluck paved the way for the composers of the Vienna Classic, such as Mozart, Salieri and Haydn.

The composer Gulio Caccini was one of the lesser-known founders of opera, but one of the most influential creators of the new Baroque style. During this time he also took part in the movement of humanists, writers, musicians and scholars who formed the Florentine Camerata, a group which gathered at the home of Count Giovanni de’Bardi, and which was dedicated to recovering the lost glory of ancient Greek drama.

Claudio Monteverdi's work, often regarded as revolutionary, marked the transition from the Renaissance style to that of the Baroque period. He developed two individual styles of composition; the heritage of Renaissance polyphony, and the new basso continuo technique of the Baroque. He was an innovative composer and enjoyed considerable fame in his lifetime.

Monteverdi’s L'Arianna  was one of the earliest operas of the Baroque period. It was first performed in 1608, as part of the musical festivities for a royal wedding at the court of Duke Vincenzo Gonzagain in Mantua. Unfortunately, all the music is lost except for anextended recitative known as Lamento d'Arianna. The opera’s subject was the ancient Greek legend of Ariadne and Theseus.

L'Incoronazione di Poppea, the lastand most innovative opera by Monteverdi, is one of the first operas to use historical events and people. It describes how Poppea, mistress of the Roman emperor Nero, is able to achieve her ambition and be crowned empress. This is one example of how historical events can become mythologized over time.The work broke new ground in matching music to stage action, and also in its musical reproduction of the natural inflections of the human voice. A musical peak is the duet Pur ti miro, Pur ti godo.