Pagliacci (Italian pronunciation: [paʎˈʎattʃi]; Players, or Clowns), sometimes incorrectly rendered with a definite article as I Pagliacci, is an opera consisting of a prologue and two acts written and composed by Ruggero Leoncavallo. It recounts the tragedy of a jealous husband in a commedia dell'arte troupe. It is the only opera of Leoncavallo's that is still widely staged.

Pagliacci premiered at the Teatro Dal Verme in Milan on May 21, 1892, conducted by Arturo Toscanini with Adelina Stehle as Nedda, Fiorello Giraud as Canio, Victor Maurel as Tonio, and Mario Ancona as Silvio. Nellie Melba played Nedda in London in 1892, soon after its Italian premiere, and in New York in 1893.

Around 1890, when Cavalleria rusticana premiered, Leoncavallo was a little-known composer. After seeing its success, he decided to write a similar opera. It was to be in one act and composed in the verismo style. A lawsuit was brought against him for plagiarism of the libretto by Catulle Mendès, whose 1887 play entitled La Femme de Tabarin shares many themes with Pagliacci, namely the play-within-the-play and the clown murdering his wife. Leoncavallo's defense was that the plot of the opera was based on a true story he had witnessed as a child. He claimed that a servant had taken him to a commedia performance in which the events of the opera had actually occurred. He also claimed that his father, who was a judge, had led the criminal investigation, and that he had documents supporting these claims but none of this evidence has ever appeared. Today most critics agree that the libretto was indeed inspired by the Mendès play since Leoncavallo was living in Paris at the time of its premiere, and it is likely that he saw the play.