Dreimal sieben Gedichte aus Albert Girauds "Pierrot lunaire" ("Three times Seven Poems from Albert Giraud's 'Pierrot lunaire'"), commonly known simply as Pierrot lunaire, Op. 21 ("Moonstruck Pierrot" or "Pierrot in the Moonlight"), is a melodrama by Arnold Schoenberg. It is a setting of 21 selected poems from Albert Giraud's cycle of the same name as translated into German by Otto Erich Hartleben. The work is written for reciter (voice-type unspecified in the score, but traditionally performed by a soprano) who delivers the poems in the Sprechstimme style accompanied by a small instrumental ensemble. Schoenberg had previously used a combination of spoken text with instrumental accompaniment, called "melodrama", in the summer-wind narrative of the Gurre-Lieder, which was a fashionable musical style popular at the end of the nineteenth century. Though the music is atonal, it does not employ Schoenberg's twelve-tone technique, which he did not use until 1921.

Pierrot lunaire is among Schoenberg's most celebrated and frequently performed works. Its instrumentation – flute, clarinet, violin, cello, and piano with standard doublings and in this case with the addition of a vocalist – is an important ensemble in 20th- and 21st-century classical music and is referred to as a Pierrot ensemble.

The piece was premiered at the Berlin Choralion-Saal on October 16, 1912, with Albertine Zehme as the vocalist. A typical performance lasts about 35 to 40 minutes. The American premiere took place at the Klaw Theatre, on Broadway, New York, on 4 February 1923 as part of a series of concerts organised by the International Composers' Guild.

The work originated in a commission by Albertine Zehme, a former actress, for a cycle for voice and piano, setting a series of poems by the Belgian writer Albert Giraud. The verses had been first published in 1884 and later translated into German by Otto Erich Hartleben. Zehme had previously performed a 'melodrama' by composer Otto Vrieslander based on the translated poems. But, according to Eduard Steuermann, student of Schoenberg and pianist of the premiere, "the music was not strong enough, and someone advised her to approach Schoenberg."

Schoenberg began work on March 12 and completed the piece on July 9, 1912, having expanded the forces to an ensemble consisting of flute (doubling on piccolo), clarinet in A (doubling on bass clarinet and clarinet in B♭), violin (doubling on viola), cello, and piano.

After forty rehearsals, Schoenberg and Zehme (in Columbine dress) gave the premiere at the Berlin Choralion-Saal on October 16, 1912. Reaction was mixed. According to Anton Webern, some in the audience were whistling and laughing, but in the end "it was an unqualified success". According to eyewitness Salka Viertel, the sister of the premiere's pianist Eduard Steuermann,

When she appeared in a Pierrot costume, her painted, frightened face framed by a ruff, her aging ankles in white stockings, she was greeted by an ominous murmur from the audience. One could not help admiring her courage, as she went on from poem to poem, disregarding the hissing, booing and insulting invective shouted at her and Schoenberg. There were also fanatical ovations from the young generation, but the majority were outraged. A well-known virtuoso, his face purple with rage, shouted: "Shoot him. Shoot him," meaning Schoenberg, not the poor, undaunted Pierrot.

There was some criticism of blasphemy in the texts, to which Schoenberg responded, "If they were musical, not a single one would give a damn about the words. Instead, they would go away whistling the tunes."