An encore is an additional performance given by performers at the conclusion of a show or concert, usually in response to extended applause from the audience. They are regarded as the most complimentary kind of applause for performers. Multiple encores are not uncommon, and they initially originated spontaneously, when audiences continued to applaud and demand additional performance from the artists after they had left the stage. However, in modern times they are rarely spontaneous and are usually a pre-planned part of the show.

Encores are believed to have originated from Italian operas in the 18th century. One of the earliest recorded encores was in 1786 at the premiere of Mozart's Marriage of Figaro. Contrary to modern encores, encores were traditionally spontaneous and followed a singular piece or movement. Performers would often perform an encore to multiple pieces within one concert; this could nearly double the length of a concert.

It is commonly believed the encores first began due to a lack of ways to listen to pieces on demand. If people wanted to listen to their favorite pieces, they would have to see them live and many rarely had the opportunity to do this. For this reason, people would demand the chance to hear a piece a second time.

At the end of a concert, if there is prolonged applause, one more relatively short piece may be performed as an encore. In some modern circumstances, encores have come to be expected, and artists often plan their encores. Traditionally, in a concert that has a printed set list for the audience, encores are not listed, even when they are planned. A well-known example is the performance of the Radetzky March and The Blue Danube at the end of the Vienna New Year's Concert by the Vienna Philharmonic Orchestra; neither piece is ever listed in the official program, but they are traditionally played every year.^{[citation needed]}

Sometimes, especially with premiers, certain movements might be applauded enough to provoke an encore of the movement. Sometimes, however, some longer and larger works will not have an encore as it is deemed inappropriate. At the first performance of Haydn's The Creation, Haydn had requested for there to not be any encores of movements out of respect for the entirety of the piece and the continuity of the work. Sometimes though, it is simply due to the conductor or artist being exhausted after a long program.

Beginning in the 18th century, if an aria was strongly applauded, it might be repeated. For example, at the premiere of Mozart's Marriage of Figaro on May 1, 1786, and other early performances, "many pieces were encored, almost doubling the length of each performance".

For "Figaro", on 9 May 1786 Emperor Joseph II of Austria issued an order limiting encores. By tradition, some world-class opera houses, such as La Scala and the Metropolitan Opera, officially discourage encores, especially for vocal solos, as encores were associated with less serious performances.

In the mid-19th century, encores were officially banned in northern Italy, since the Austrian-Italian authorities felt that they would lead to public disorder. In 1921, encores were forbidden at La Scala in Milan, Italy because the conductor Toscanini felt they would interrupt the pace of the opera and drew attention to individual singers as opposed to the work. Toscanini had, in 1887, been challenged to a duel after stubbornly refusing an aria's encore. Richard Wagner was similarly against encores.