Don Giovanni (Italian pronunciation: [ˈdɔn dʒoˈvanni]; K. 527; full title: Il dissoluto punito, ossia il Don Giovanni, literally The Rake Punished, or Don Giovanni) is an opera in two acts with music by Wolfgang Amadeus Mozart to an Italian libretto by Lorenzo Da Ponte. Its subject is a centuries-old Spanish legend about a libertine as told by playwright Tirso de Molina in his 1630 play El burlador de Sevilla y convidado de piedra. It is a dramma giocoso blending comedy, melodrama and supernatural elements (although the composer entered it into his catalogue simply as opera buffa). It was premiered by the Prague Italian opera at the National Theatre (of Bohemia), now called the Estates Theatre, on 29 October 1787. Don Giovanni is regarded as one of the greatest operas of all time and has proved a fruitful subject for commentary in its own right; critic Fiona Maddocks has described it as one of Mozart's "trio of masterpieces with librettos by Da Ponte".

The opera was commissioned after the success of Mozart's trip to Prague in January and February 1787. The subject may have been chosen because the sub-genre of Don Juan opera originated in that city. Lorenzo Da Ponte's libretto is based on Giovanni Bertati's for the opera Don Giovanni Tenorio, which premiered in Venice early in 1787. In two aspects he copied Bertati: by opening with the Commendatore's murder and by avoiding mention of Seville (for Bertati the setting was Villena, Spain; Da Ponte simply writes "city in Spain").

The opera was supposed to premiere on 14 October 1787 for Archduchess Maria Theresa of Austria's visit, but it was not ready in time and Le nozze di Figaro was substituted. Mozart recorded its completion, finally, on 28 October, the night before the premiere (29 October).

The opera was rapturously received, as was often true of Mozart's work in Prague. The Prager Oberpostamtzeitung reported, "Connoisseurs and musicians say that Prague has never heard the like", and "the opera ... is extremely difficult to perform." The Provincialnachrichten of Vienna reported, "Herr Mozart conducted in person and was welcomed joyously and jubilantly by the numerous gathering."

The score calls for double woodwinds, two horns, two trumpets, three trombones (at the end of Act II only, alto, tenor, bass), timpani, basso continuo for the recitatives, and the usual string section. The composer also specified occasional special musical effects. For the ballroom scene at the end of the first act, Mozart calls for two onstage ensembles to play separate dance music in synchronization with the pit orchestra, each of the three groups playing in its own metre (a 3/4 minuet, a 2/4 contradanse and a fast 3/8 peasant dance), accompanying the dancing of the principal characters. In act 2, Giovanni is seen to play the mandolin, accompanied by pizzicato strings. In the same act, two of the Commendatore's interventions ("Di rider finirai pria dell'aurora" and "Ribaldo, audace, lascia a' morti la pace") are accompanied by a wind chorale of oboes, clarinets, bassoons, and trombones (with cellos and basses playing from the string section).

Mozart also supervised the Vienna premiere of the work, which took place on 7 May 1788. For this production, he wrote two new arias with corresponding recitatives – Don Ottavio's aria "Dalla sua pace" (K. 540a, composed on 24 April for the tenor Francesco Morella), Elvira's aria "In quali eccessi ... Mi tradì quell'alma ingrata" (K. 540c, composed on 30 April for the soprano Caterina Cavalieri) – and the duet between Leporello and Zerlina "Per queste tue manine" (K. 540b, composed on 28 April). He also made some cuts in the Finale in order to make it shorter and more incisive, the most important of which is the section where Anna and Ottavio, Elvira, Zerlina and Masetto, Leporello reveal their plans for the future ("Or che tutti, o mio tesoro"). In order to connect "Ah, certo è l'ombra che l'incontrò" ("It must have been the ghost she met") directly to the moral of the story "Questo è il fin di chi fa mal" ("This is the end which befalls to evildoers"), Mozart composed a different version of "Resti dunque quel birbon fra Proserpina e Pluton!" ("So the wretch can stay down there with Proserpina and Pluto!"). These cuts are very seldom performed in theatres or recordings.

The opera's final ensemble was generally omitted until the early 20th century, a tradition that apparently began very early on. According to the 19th-century Bohemian memoirist Wilhelm Kuhe, the final ensemble was only presented at the first performance in Prague, then never heard again during the original run. It does not appear in the Viennese libretto of 1788; thus the ending of the first performance in Vienna without the ensemble as depicted in the film Amadeus may be an accurate portrayal. Nonetheless, the final ensemble is almost invariably performed in full today.

Modern productions sometimes include both the original aria for Don Ottavio, "Il mio tesoro", and its replacement from the first production in Vienna that was crafted to suit the capabilities of the tenor Francesco Morella, "Dalla sua pace". Elvira's "In quali eccessi, o Numi ... Mi tradì quell'alma ingrata" is usually retained as well. The duet "Per queste tue manine" and the whole accompanying scene involving Zerlina and Leporello from the Viennese version is almost never included.^{[failed verification]}