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 travelled 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 portions of the Requiem, which was largely unfinished at the time of Mozart's death. 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. At the time it was part of the Bavarian Circle in the Holy Roman Empire. His only sibling to survive past birth was Maria Anna (1751–1829), called "Nannerl". Wolfgang was baptized the day after his birth at St. Rupert's Cathedral. The baptismal record gives his name in Latinized form as Joannes Chrysostomus Wolfgangus Theophilus Mozart. He generally called himself "Wolfgang Amadè Mozart" as an adult, but there were many variants.

His father Leopold (1719–1787) was from Augsburg and deputy Kapellmeister to the court orchestra of the Archbishop of Salzburg, and a minor composer. He was also an experienced teacher. In the year of Mozart's birth, his father published a violin textbook, Versuch einer gründlichen Violinschule, which achieved success.

When Nannerl was seven she began keyboard lessons with her father, and her three-year-old brother would look on, evidently fascinated. Years later, after his death, she reminisced:

He often spent much time at the clavier, picking out thirds, which he was always striking, and his pleasure showed that it sounded good. [...] In the fourth year of his age his father, for a game as it were, began to teach him a few minuets and pieces at the clavier. [...] He could play it faultlessly and with the greatest delicacy, and keeping exactly in time. [...] At the age of five he was already composing little pieces, which he played to his father who wrote them down.

These early pieces, K. 1–5, were recorded in the Nannerl Notenbuch.

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 youth, his family made several European journeys in which he and 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.

These trips were often arduous. Travel conditions were primitive, the family had to wait for invitations and reimbursement from the nobility. They endured long, near-fatal illnesses far from home: first Leopold (London, summer 1764) then both children (The Hague, autumn 1765).