Austrian composer. Intended for the priesthood, he was recruited at age eight to the choir at St. Stephen's Cathedral, Vienna, where he learned violin and keyboard. On leaving the choir, he began supporting himself by teaching and playing violin, while undertaking a rigorous study of counterpoint and harmony. He came to the attention of Pietro Metastasio and through him became factotum to the composer Nicola Porpora in exchange for lessons. Gaining entrée to high society, in 1761 he became head of the musical establishment at the great palace of the Esterházy family, which would support him for most of his career. In this position of artistic isolation but with excellent resources, Haydn felt free to experiment and was forced to become original. By his late years he was recognized internationally as the greatest living composer. He composed important works in almost every genre, and his elegant and ingratiating works balance wit and seriousness, custom and innovation. The first great symphonist, he composed 106 symphonies, including the popular last 12 "London symphonies" (1791 – 95). He virtually invented the string quartet, and his 68 quartets remain the foundation of the quartet literature. His choral works include 14 masses and the oratorios The Creation (1798) and The Seasons (1801). He also wrote 47 piano sonatas and more than 125 beautiful works for the cello-like baryton. The principal shaper of the Classical style, he exerted major influence on his friend Wolfgang Amadeus Mozart and on his student Ludwig van Beethoven.

He struggled in poverty for years, earning a meager living as a teacher and accompanist. Eventually, his compositions came to the attention of some of Vienna's music-loving aristocrats, and under their patronage his career progressed rapidly. Most of his prodigious musical output was produced during the 29 years of his service as musical director to the princes Esterházy, beginning in 1761. During the 1780s, when he received commissions from London and Paris and honors from all over Europe, he formed a close friendship with Mozart, an association that influenced the music of each. In 1791 and 1794 he made lucrative visits to London, where he held concerts featuring his own music. During this period he wrote the 12 so-called Salomon Symphonies (after the impresario who had arranged his tours), much chamber music, and a large number of songs with English texts. Haydn's works are notable for their originality, liveliness, optimism, and instrumental brilliance. He established the basic forms of symphonic music and string quartet, which were to be a model and inspiration for the works of Mozart, and of Beethoven, who studied under Haydn. Important in the development of the classic sonata form, his string quartets and symphonies expanded the three-movement sonata form of C. P. E. Bach, adding one or two minuets before the last movement. Two great oratorios, The Creation (1798) and The Seasons (1801), were written in his old age. His works include over 100 symphonies, many known by such names as the Farewell Symphony (1772), the Surprise Symphony (1791), the Military Symphony (1794), and the Clock Symphony (1794); over 80 string quartets; much other chamber music; more than 50 piano sonatas; and numerous operas, masses, and songs.