The Nutcracker (Russian: Щелкунчик, Shchelkunchik) Op. 71, is a fairy tale-ballet in two acts, three scenes, by Pyotr Ilyich Tchaikovsky, composed in 1891–92. Alexandre Dumas père's adaptation of the story by E. T. A. Hoffmann was set to music by Tchaikovsky (written by Marius Petipa and commissioned by the director of the Imperial Theatres Ivan Vsevolozhsky in 1891). In Western countries, this ballet has become perhaps the most popular ballet performed, primarily around Christmas time.

The composer made a selection of eight of the more popular numbers from the ballet before the ballet's December 1892 premiere, forming The Nutcracker Suite, Op. 71a, intended for concert performance. The suite was first performed, under the composer's direction, on 19 March 1892 at an assembly of the St. Petersburg branch of the Musical Society. The suite became instantly popular; the complete ballet did not achieve its great popularity until around the mid-1960s.

Among other things, the score of The Nutcracker is noted for its use of the celesta, an instrument that the composer had already employed in his much lesser known symphonic poem The Voyevoda (premiered 1891). Although well-known in The Nutcracker as the featured solo instrument in the "Dance of the Sugar Plum Fairy" from Act II, it is employed elsewhere in the same act.

The story has been published in many book versions including colourful children-friendly versions. The plot revolves around a German girl named Clara Stahlbaum or Clara Silverhaus. In some Nutcracker productions, Clara is called Marie. (In Hoffmann's tale, the girl's name actually is Marie or Maria, while Clara - or "Klärchen" - is the name of one of her dolls.)

The work opens with a brief “Miniature Overture”, which also opens the Suite. The music sets the fairy mood by using upper registers of the orchestra exclusively. The curtain opens to reveal the Stahlbaums' house, where a Christmas Eve party is under way. Clara, her little brother Fritz, and their mother and father are celebrating with friends and family, when the mysterious godfather, Herr Drosselmeyer, enters. He quickly produces a large bag of gifts for all the children. All are very happy, except for Clara, who has yet to be presented a gift. Herr Drosselmeyer then produces three life-size dolls, which each take a turn to dance. When the dances are done, Clara approaches Herr Drosselmeyer asking for her gift. It would seem that he is out of presents, and Clara runs to her mother in a fit of tears and disappointment.

Drosselmeyer then produces a toy Nutcracker, in the traditional shape of a soldier in full parade uniform. Clara is overjoyed, but her brother Fritz is jealous, and breaks the Nutcracker.

The party ends and the Stahlbaum family go to bed. While everybody is sleeping, Herr Drosselmeyer repairs the Nutcracker. Then Clara wakes up and sees her window open. When the clock strikes midnight, Clara hears the sound of mice. She wakes up and tries to run away, but the mice stop her. Alternatively, perhaps Clara is still in a dream: the Christmas tree suddenly begins to grow to enormous size, filling the room. The Nutcracker comes to life, he and his band of soldiers rise to defend Clara, and the Mouse King leads his mice into battle. Here Tchaikovsky continues the miniature effect of the Overture, setting the battle music predominantly in the orchestra's upper registers.

A conflict ensues, and when Clara helps the Nutcracker by holding the Mouse King by the tail or throwing her shoe at the Mouse King, the Nutcracker seizes his opportunity and stabs him. The mouse dies. The mice retreat, taking their dead leader with them. The Nutcracker is then transformed into a prince. (In Hoffmann's original story, and in the Royal Ballet's 1985 and 2001 versions, the Prince is actually Drosselmeyer's nephew, who had been turned into a Nutcracker by the Mouse King, and all the events following the Christmas party have been arranged by Drosselmeyer in order to break the spell.)

Clara and the Prince travel to a world where dancing Snowflakes greet them and fairies and queens dance, welcoming Clara and the Prince into their world. The score conveys the wondrous images by introducing a wordless children’s chorus. The curtain falls on Act I.

Clara and the Prince arrive at the Land of the Sugar Plum Fairy. The Sugar Plum Fairy and the people of the Land of Sweets dance for Clara and the Prince in the dances of Dew Drop Fairy, the Spanish dancers (sometimes Chocolate), the Chinese dancers (sometimes Tea), the Arabian dancers (sometimes Coffee), the Russian dancers (sometimes Candy Canes--their dance is called the Trepak), Mother Ginger and her Polichinelles (sometimes Bonbons, Taffy Clowns, or Court Buffoons in Baryshnikov's production), the Reed Flutes (sometimes Marzipan shepherds or Mirlitons), the Sugar Plum Fairy, and the Waltz of the Flowers. The dances in the Land of the Sugar Plum Fairy are not always performed in this order.

After the festivities, Clara wakes up under the Christmas tree with the Nutcracker toy in her arms and the curtain closes. (In Balanchine's version, however, she is never shown waking up; instead, after all the dances in the Kingdom of Sweets have concluded, she rides off with the Nutcracker/Prince on a Santa Claus-like flying sleigh, complete with reindeer, and the curtain falls. This gives the impression that the "dream" actually happens in reality, as in Hoffmann's original story. The 1985 Royal Ballet version seems to imply the same thing, since at the end, Drosselmeyer's nephew, who had really been transformed into a nutcracker, reappears in human form at the toymaker's shop.)