Wolfgang Amadeus Mozart, full baptismal name Johannes Chrysostomus Wolfgangus Theophilus Mozart (27 January 1756 – 5 December 1791), was a prolific and influential composer of the Classical era. He composed over 600 works, many acknowledged as pinnacles of symphonic, concertante, chamber, piano, operatic, and choral music. He is among the most enduringly popular of classical composers.

Mozart showed prodigious ability from his earliest childhood in Salzburg. Already competent on keyboard and violin, he composed from the age of five and performed before European royalty; at 17 he was engaged as a court musician in Salzburg, but grew restless and traveled in search of a better position, always composing abundantly. While visiting Vienna in 1781, he was dismissed from his Salzburg position. He chose to stay in the capital, where he achieved fame but little financial security. During his final years in Vienna, he composed many of his best-known symphonies, concertos, and operas, and the Requiem. The circumstances of his early death have been much mythologized. He was survived by his wife Constanze and two sons.

Mozart learned voraciously from others, and developed a brilliance and maturity of style that encompassed the light and graceful along with the dark and passionate. His influence on subsequent Western art music is profound.Beethoven wrote his own early compositions in the shadow of Mozart, of whom Joseph Haydn wrote that "posterity will not see such a talent again in 100 years."

Wolfgang Amadeus Mozart was born to Leopold and Anna Maria Pertl Mozart at 9 Getreidegasse in Salzburg, capital of the sovereign Archbishopric of Salzburg, in what is now Austria. Then it was part of the Holy Roman Empire. His father Leopold (1719–1787) was deputy Kapellmeister to the court orchestra of the Archbishop of Salzburg, and a minor composer. He was also an experienced teacher. Biographer Maynard Solomon notes that while Leopold was a devoted teacher to his children, there is evidence that Wolfgang was keen to make progress beyond what he was being taught. His first ink-spattered composition and his precocious efforts with the violin were on his own initiative, and came as a great surprise to Leopold. Leopold eventually gave up composing when his son's outstanding musical talents became evident. He was Wolfgang's only teacher in his earliest years, and taught his children languages and academic subjects as well as music.

During Mozart's formative years, his family made several European journeys in which he and his sister Nannerl performed as child prodigies. These began with an exhibition in 1762 at the court of the Prince-elector Maximilian III of Bavaria in Munich, then in the same year at the Imperial Court in Vienna and Prague. A long concert tour spanning three and a half years followed, taking the family to the courts of Munich, Mannheim, Paris, London, The Hague, again to Paris, and back home via Zürich, Donaueschingen, and Munich. During this trip Mozart met a great number of musicians and acquainted himself with the works of other composers. A particularly important influence was Johann Christian Bach, whom Mozart visited in London in 1764 and 1765. The family again went to Vienna in late 1767 and remained there until December 1768.

After one year in Salzburg, father and son set off for Italy, leaving Wolfgang's mother and sister at home. This travel lasted from December 1769 to March 1771. As with earlier journeys, Leopold wanted to display his son's abilities as a performer and as a rapidly maturing composer. Wolgang Mozart met G. B. Martini and Josef Mysliveček in Bologna and was accepted as a member of the famous Accademia Filarmonica. In Rome he heard Gregorio Allegri's Miserere once in performance in the Sistine Chapel. He wrote it out in its entirety from memory, only returning to correct minor errors—thus producing the first illegal copy of this closely guarded property of the Vatican. In Milan, Mozart wrote the opera Mitridate, re di Ponto (1770), which was performed with success. This led to further opera commissions. He returned with his father later twice to Milan (August–December 1771; October 1772 – March 1773) for the composition and premieres of Ascanio in Alba (1771) and Lucio Silla (1772). 
Toward the end of the final Italian journey, Mozart wrote the first of his works to be still widely performed today, the solo cantata Exsultate, jubilate, K. 165.

After finally returning with his father from Italy on 13 March 1773, Mozart was employed as a court musician by the ruler of Salzburg Prince-Archbishop Hieronymus Colloredo.  Between April and December of 1775, Mozart developed an enthusiasm for violin concertos, producing a series of five (the only ones he ever wrote), which steadily increase in their musical sophistication. In 1776 he turned his efforts to piano concertos, culminating in the E-flat concerto K. 271 of early 1777.

Despite these artistic successes, Mozart grew increasingly discontent with Salzburg and redoubled his efforts to find a position elsewhere. One reason was his low salary; but also, Mozart longed to compose operas, and Salzburg provided only rare occasions for these. The situation worsened in 1775 when the court theater was closed, especially since the other theater in Salzburg was largely reserved for visiting troupes. Two long expeditions in search of work (both Leopold and Wolfgang were looking) interrupted this long Salzburg stay: they visited Vienna from 14 July to 26 September 1773, and Munich from 6 December 1774 to March 1775. Neither visit was successful, though the Munich journey resulted in a popular success with the premiere of Mozart's opera La finta giardiniera.

In August 1777, Mozart resigned his Salzburg position and on 23 September ventured out once more in search of employment, with visits to Augsburg, Mannheim, Paris, and Munich. Since Archbishop Colloredo would not give Leopold leave to travel, Mozart's mother Anna Maria was assigned to accompany him. Mozart became acquainted with members of the famous orchestra in Mannheim, the best in Europe at the time. He also fell in love with Aloysia Weber, one of four daughters in a musical family. There were some prospects of employment in Mannheim, but they came to nothing; and Mozart left for Paris on 14 March 1778 to continue his search. There his luck was hardly better; one of his letters home hints at a possible post as an organist at Versailles, but Mozart was not interested in such an appointment. He fell into debt and took to pawning valuables. The nadir of the visit occurred when Mozart's mother took ill, and died on 3 July 1778. There had been delays in calling a doctor—probably, according to Halliwell, because of a lack of funds. While Wolfgang was in Paris, Leopold was energetically pursuing opportunities for him back in Salzburg, and with the support of local nobility secured him a better post as court organist and concertmaster. Wolfgang was reluctant to accept, and after leaving Paris on 26 September 1778 he tarried in Mannheim and Munich, still hoping to obtain an appointment outside Salzburg. In Munich he again encountered Aloysia, now a very successful singer: but she made it plain that she was no longer interested in him. Mozart finally reached home on 15 January 1779 and took up the new position, but his discontent with Salzburg was undiminished.

In January 1781, Mozart's opera Idomeneo premiered with "considerable success" in Munich. The following March the composer was summoned to Vienna, where his employer, Archbishop Colloredo, was attending the celebrations for the accession of Joseph II to the Austrian throne. Mozart, fresh from the adulation he had earned in Munich, was offended when Colloredo treated him as a mere servant, and particularly when the archbishop forbade him to perform before the Emperor at Countess Thun's for a fee equal to half of his yearly Salzburg salary. The resulting quarrel came to a head in May: Mozart attempted to resign, and was refused. The following month permission was granted, but in a grossly insulting way: the composer was dismissed literally "with a kick in the ass", administered by the archbishop's steward, Count Arco. In Vienna, though, Mozart had become aware of some rich opportunities, and he decided to settle there as a freelance performer and composer.

The quarrel with the archbishop went harder for Mozart because his father sided against him. Hoping fervently that he would obediently follow Colloredo back to Salzburg, Leopold exchanged intense letters with his errant son, urging him to be reconciled with their employer; but Wolfgang passionately defended his intention to pursue an independent career in Vienna. The debate ended when Mozart was dismissed, freeing him from the demands of an oppressive employer and of an over-solicitous father. Solomon characterizes Mozart's resignation as a "revolutionary step", and it greatly altered the course of his life.

Mozart's new career in Vienna began well. He performed often as a pianist, notably in a competition before the Emperor with Muzio Clementi on 24 December 1781, and he soon "had established himself as the finest keyboard player in Vienna". He also prospered as a composer, and in 1782 completed the opera Die Entführung aus dem Serail ("The Abduction from the Seraglio"), which premiered on 16 July 1782 to enormous acclaim. Near the height of his quarrels with Colloredo, Mozart moved in with the Weber family, who had moved to Vienna from Mannheim. The father, Fridolin, had died, and the Webers were now taking in lodgers to make ends meet. Aloysia, who had earlier rejected Mozart's suit, was now married to the actor Joseph Lange, and Mozart's interest shifted to the third daughter, Constanze. The couple were married on 4 August 1782.

In the course of 1782 and 1783 Mozart became intimately acquainted with the work of Johann Sebastian Bach and George Frideric Handel as a result of the influence of Gottfried van Swieten, who owned many manuscripts of the Baroque masters. Mozart's study of these scores inspired compositions in Baroque style, and later had a powerful influence on his own personal musical language: for example in fugal passages in Die Zauberflöte ("The Magic Flute") and the finale of Symphony No. 41. In 1783, Wolfgang and Constanze visited his family in Salzburg. Leopold and Nannerl were, at best, only polite to Constanze; but the visit at least prompted the composition of one of Mozart's great liturgical pieces, the Mass in C minor. Mozart met Joseph Haydn in Vienna, and the two composers became friends (see Haydn and Mozart). When Haydn visited Vienna, they sometimes played together in an impromptu string quartet. Mozart's six quartets dedicated to Haydn date from the period 1782 to 1785, and amount to a carefully considered response to Haydn's Opus 33 set from 1781. From 1782 to 1785 Mozart mounted concerts with himself as soloist, presenting three or four new piano concertos in each season. The concerts were very popular, and the concertos he premiered at them are still firm fixtures in the repertoire. 

With substantial returns from his concerts and elsewhere, he and Constanze adopted a rather plush lifestyle. They moved to an expensive apartment. Mozart also bought a fine forte piano from Anton Walter and a billiard table. The Mozarts sent their son Karl Thomas to an expensive boarding school and kept servants. Saving was therefore impossible, and the short period of financial success did nothing to soften the hardship the Mozarts were later to experience.

On 14 December 1784, Mozart became a Freemason, admitted to the lodge Zur Wohltätigkeit ("Beneficence"). Freemasonry played an important role in the remainder of Mozart's life: he attended many meetings, a number of his friends were Masons, and on various occasions he composed Masonic music. (See Mozart and Freemasonry.)

Despite the great success of Die Entführung aus dem Serail, Mozart did little operatic writing for the next four years, producing only two unfinished works and the one-act Der Schauspieldirektor. He focused instead on his career as a piano soloist and writer of concertos. However, around the end of 1785, Mozart moved away from keyboard writing and began his famous operatic collaboration with the librettist Lorenzo Da Ponte. 1786 saw the successful premiere of The Marriage of Figaro in Vienna. Its reception in Prague later in the year was even warmer, and this led to a second collaboration with Da Ponte: the opera Don Giovanni, which premiered in October 1787 to acclaim in Prague, and also met with success in Vienna in 1788. These developments were not witnessed by the composer's father, as Leopold had died on 28 May 1787.

In December 1787 Mozart finally obtained a steady post under aristocratic patronage. Emperor Joseph II appointed him as his "chamber composer", a post that had fallen vacant the previous month on the death of Gluck. It was a part-time appointment and only required Mozart to compose dances for the annual balls in the Redoutensaal. Court records show that Joseph's aim was to keep the esteemed composer from leaving Vienna in pursuit of better prospects. In 1787 the young Ludwig van Beethoven spent two weeks in Vienna, hoping to study with Mozart. Toward the end of the decade, Mozart's circumstances worsened. Around 1786 he had ceased to appear frequently in public concerts, and his income shrank. This was a difficult time for all musicians in Vienna because Austria was at war, and both the general level of prosperity and the ability of the aristocracy to support music had declined. By mid-1788, Mozart and his family had moved from central Vienna to the suburb of Alsergrund. Mozart began to borrow money, most often from his friend and fellow Mason Michael Puchberg; "a pitiful sequence of letters pleading for loans" survives. Major works of the period include the last three symphonies (Nos. 39, 40, and 41, all from 1788, and the last of the three Da Ponte operas, Così fan tutte, premiered in 1790. Around this time Mozart made long journeys hoping to improve his fortunes: to Leipzig, Dresden, and Berlin in the spring of 1789, and to Frankfurt, Mannheim, and other German cities in 1790. The trips produced only isolated success and did not relieve the family's financial distress.

Mozart's last year was, until his final illness struck, a time of great productivity—and by some accounts a time of personal recovery. He composed a great deal, including some of his most admired works: the opera The Magic Flute, the final piano concerto, the Clarinet Concerto K. 622, the last in his great series of string quintets, the motet Ave verum corpus K. 618, and the unfinished Requiem K. 626. Mozart's financial situation, a source of extreme anxiety in 1790, finally began to improve. Although the evidence is inconclusive it appears that wealthy patrons in Hungary and Amsterdam pledged annuities to Mozart, in return for the occasional composition. He probably also benefited from the sale of dance music written in his role as Imperial chamber composer. Mozart no longer borrowed large sums from Puchberg, and made a start on paying off his debts.

Mozart fell ill while in Prague, for the premiere on 6 September of his opera La clemenza di Tito, written in 1791 on commission for the Emperor's coronation festivities. He was able to continue his professional functions for some time, and conducted the premiere of The Magic Flute on 30 September. The illness intensified on 20 November, at which point Mozart became bedridden, suffering from swelling, pain, and vomiting. Mozart was nursed in his final illness by Constanze and her youngest sister Sophie, and attended by the family doctor, Thomas Franz Closset. It is clear that he was mentally occupied with the task of finishing his Requiem. Mozart died at 1 a.m. on 5 December 1791 at the age of 35.