La fanciulla del West (The Girl of the West) is an opera in three acts by Giacomo Puccini to an Italian libretto by Guelfo Civinini (it) and Carlo Zangarini, based on the play The Girl of the Golden West by the American author David Belasco. Fanciulla followed Madama Butterfly, which was also based on a Belasco play. The opera has fewer of the show-stopping highlights that are characteristic of other Puccini works, but is admired for its impressive orchestration and for a score that is more melodically integrated than is typical of his previous work. Fanciulla displays influences from composers Claude Debussy, Igor Stravinsky and Richard Strauss, without being in any way imitative. Similarities between the libretto and the work of Richard Wagner have also been found, though some attribute this more to the original plot of the play, and have asserted that the opera remains quintessentially Italian.

The opera had a successful and highly-publicised première at the Met in 1910. Nevertheless, while Puccini deemed it one of his greatest works, La fanciulla del West has become a less popular opera within the composer's repertoire, drawing a mixed public reception overall. Despite the plot being a source of significant criticism, the majority of academics and musicians agree in calling it a magnum opus, particularly lauding its craftmanship. Conductor Arturo Toscanini called the opera a "great symphonic poem".