Opera seria (Italian pronunciation: [ˈɔːpera ˈsɛːrja]; plural: opere serie; usually called dramma per musica or melodramma serio) is an Italian musical term which refers to the noble and "serious" style of Italian opera that predominated in Europe from the 1710s to about 1770. The term itself was rarely used at the time and only attained common usage once opera seria was becoming unfashionable and beginning to be viewed as something of a historical genre. The popular rival to opera seria was opera buffa, the 'comic' opera that took its cue from the improvisatory commedia dell'arte.

Italian opera seria (invariably to Italian libretti) was produced not only in Italy but almost throughout Europe, and beyond (see Opera in Latin America, Opera in Cuba e. g.). Among the main centres in Europe were the court operas based in Warsaw (since 1628), Munich (founded in 1653), London (established in 1662), Vienna (firmly established 1709; first operatic representation: Il pomo d'oro, 1668), Dresden (since 1719) as well as other German residences, Saint Petersburg (Italian opera reached Russia in 1731, first opera venues followed c. 1742), Madrid (see Spanish opera), and Lisbon. Opera seria was less popular in France, where the national genre of French opera (or tragédie en musique) was preferred.

Acclaimed composers of opera seria included Antonio Caldara, Alessandro Scarlatti, George Frideric Handel, Antonio Vivaldi, Nicola Porpora, Leonardo Vinci, Johann Adolph Hasse, Leonardo Leo, Baldassare Galuppi, Francesco Feo, Giovanni Battista Pergolesi and in the second half of the 18th century Christoph Willibald Gluck, Niccolò Jommelli, Tommaso Traetta, Josef Mysliveček, Joseph Haydn, Johann Christian Bach, Carl Heinrich Graun, Antonio Salieri, Antonio Sacchini, Giuseppe Sarti, Niccolò Piccinni, Giovanni Paisiello, Domenico Cimarosa, and Wolfgang Amadeus Mozart. By far the most successful librettist of the era was Metastasio, others were Apostolo Zeno, Benedetto Pamphili, Silvio Stampiglia, Antonio Salvi, Pietro Pariati, Pietro Ottoboni, Stefano Benedetto Pallavicino, Nicola Francesco Haym, Domenico Lalli, Paolo Antonio Rolli, Giovanni Claudio Pasquini, Ranieri de' Calzabigi and Giovanni Ambrogio Migliavacca.