Franz Joseph Haydn (March 31, 1732 – May 31, 1809) was an Austrian composer. He was one of the most important, prolific and prominent composers of the classical period. He is often called the "Father of the Symphony" and "Father of the String Quartet" because of his important contributions to these genres. He was also instrumental in the development of the piano trio and in the evolution of sonata form.

A life-long resident of Austria, Haydn spent much of his career as a court musician for the wealthy Hungarian aristocratic Esterházy family on their remote estate. Isolated from other composers and trends in music until the later part of his long life, he was, as he put it, "forced to become original". At the time of his death, he was one of the most celebrated composers in Europe. Joseph Haydn was the brother of Michael Haydn, himself a highly regarded composer, and Johann Evangelist Haydn, a tenor. He was also a close friend of Wolfgang Amadeus Mozart and a teacher of Ludwig van Beethoven.

Joseph Haydn was born in Rohrau, Austria, a village near the border with Hungary. His father was Mathias Haydn, a wheelwright who also served as "Marktrichter", an office akin to village mayor. Haydn's mother Maria, née Koller, had previously worked as a cook in the palace of Count Harrach, the presiding aristocrat of Rohrau. Neither parent could read music; however, Mathias was an enthusiastic folk musician, who during the journeyman period of his career had taught himself to play the harp. According to Haydn's later reminiscences, his childhood family was extremely musical, and frequently sang together and with their neighbours. Haydn's parents had noticed that their son was musically gifted and knew that in Rohrau he would have no chance to obtain any serious musical training. It was for this reason that they accepted a proposal from their relative Johann Matthias Frankh, the schoolmaster and choirmaster in Hainburg, that Haydn be apprenticed to Frankh in his home to train as a musician. Haydn therefore went off with Frankh to Hainburg (seven miles away) and never again lived with his parents. He was six years old. Life in the Frankh household was not easy for Haydn, who later remembered being frequently hungry as well as constantly humiliated by the filthy state of his clothing. However, he did begin his musical training there, and soon was able to play both harpsichord and violin. The people of Hainburg were soon hearing him sing treble parts in the church choir.

There is reason to think that Haydn's singing impressed those who heard him, because he was soon brought to the attention of Georg von Reutter, the director of music in St. Stephen's Cathedral in Vienna, who happened to be visiting Hainburg. Haydn passed his audition with Reutter, and in 1740 moved to Vienna, where he worked for the next nine years as a chorister, after 1745 in the company of his younger brother Michael. Haydn lived in the Kapellhaus next to the cathedral, along with Reutter, Reutter's family, and the other four choirboys. He was instructed in Latin and other school subjects as well as voice, violin, and keyboard. Reutter was of little help to Haydn in the areas of music theory and composition, giving him only two lessons in his entire time as chorister. However, since St. Stephen's was one of the leading musical centers in Europe, Haydn was able to learn a great deal simply by serving as a professional musician there. Like Frankh before him, Reutter did not always bother to make sure Haydn was properly fed. As he later told his biographer Albert Christoph Dies, Haydn was motivated to sing very well, in hopes of gaining more invitations to perform before aristocratic audiences—where the singers were usually served refreshments. By 1749, Haydn had finally matured physically to the point that he was no longer able to sing high choral parts -- the Empress herself complained to Reutter about his singing, calling it "crowing". One day, Haydn carried out a prank, snipping off the pigtail of a fellow chorister. This was enough for Reutter: Haydn was first caned, then summarily dismissed and sent into the streets with no home to go to.

However, he had the good fortune to be taken in by a friend, Johann Michael Spangler, who for a few months shared with Haydn his family's crowded garret room. Haydn was able to begin immediately his pursuit of a career as a freelance musician. During this arduous time, Haydn worked at many different jobs: as a music teacher, as a street serenader, and eventually, in 1752, as valet–accompanist for the Italian composer Nicola Porpora, from whom he later said he learned "the true fundamentals of composition".

When he was a chorister, Haydn had not received serious training in music theory and composition, which he perceived as a serious gap. To fill it, he worked his way through the counterpoint exercises in the text Gradus ad Parnassum by Johann Joseph Fux, and carefully studied the work of Carl Philipp Emanuel Bach, whom he later acknowledged as an important influence.

As his skills increased, Haydn began to acquire a public reputation, first as the composer of an opera, Der krumme Teufel "The Limping Devil", written for the comic actor Johann Joseph Felix Kurz, whose stage name was "Bernardon". The work was premiered successfully in 1753, but was soon closed down by the censors. Haydn also noticed, apparently without annoyance, that works he had simply given away were being published and sold in local music shops. Between 1754 and 1756 Haydn also worked freelance for the court in Vienna. He was among several musicians who were paid for services as supplementary musicians at balls given for the imperial children during carnival season, and as supplementary singers in the imperial chapel (the Hofkapelle) in Lent and Holy Week.

With the increase in his reputation, Haydn eventually was able to obtain aristocratic patronage, crucial for the career of a composer in his day. Countess Thun, having seen one of Haydn's compositions, summoned him and engaged him as her singing and keyboard teacher. In 1756, Baron Carl Josef Fürnberg employed Haydn at his country estate, Weinzierl, where the composer wrote his first string quartets. Fürnberg later recommended Haydn to Count Morzin, who, in 1757, became his first full time employer. Haydn's job title under Count Morzin was Kapellmeister, that is, music director. He led the count's small orchestra and wrote his first symphonies for this ensemble. In 1760, with the security of a Kapellmeister position, Haydn married. His wife was the former Maria Anna Aloysia Apollonia Keller (1729–1800), the sister of Therese (b. 1733), with whom Haydn had previously been in love. Haydn and his wife had a completely unhappy marriage, from which the laws of the time permitted them no escape; and they produced no children. Both took lovers. Count Morzin soon suffered financial reverses that forced him to dismiss his musical establishment, but Haydn was quickly offered a similar job (1761) as Vice Kapellmeister to the Esterházy family, one of the wealthiest and most important in the Austrian Empire. When the old Kapellmeister, Gregor Werner, died in 1766, Haydn was elevated to full Kapellmeister. As a "house officer" in the Esterházy establishment, Haydn wore livery and followed the family as they moved among their various palaces, most importantly the family's ancestral seat Schloss Esterházy in Eisenstadt and later on Eszterháza, a grand new palace built in rural Hungary in the 1760s. Haydn had a huge range of responsibilities, including composition, running the orchestra, playing chamber music for and with his patrons, and eventually the mounting of operatic productions. Despite this workload, the job was in artistic terms a superb opportunity for Haydn. The Esterházy princes (first Paul Anton, then most importantly Nikolaus I) were musical connoisseurs who appreciated his work and gave him daily access to his own small orchestra. During the nearly thirty years that Haydn worked at the Esterházy court, he produced a flood of compositions, and his musical style continued to develop. His popularity in the outside world also increased. Gradually, Haydn came to write as much for publication as for his employer, and several important works of this period, such as the Paris symphonies (1785–1786) and the original orchestral version of The Seven Last Words of Christ (1786), were commissions from abroad. Haydn also gradually came to feel more isolated and lonely, particularly as the court came to spend most of the year at Esterháza, far from Vienna, rather than the closer-by Eisenstadt. Haydn particularly longed to visit Vienna because of his friendships there.

Of these, a particularly important one was with Maria Anna von Genzinger (1750–93), the wife of Prince Nikolaus's personal physician in Vienna, who began a close, platonic, relationship with the composer in 1789. Haydn wrote to Mrs. Genzinger often, expressing his loneliness at Eszterháza and his happiness for the few occasions on which he was able to visit her in Vienna; later on, Haydn wrote to her frequently from London. Her premature death in 1793 was a blow to Haydn, and his F minor variations for piano, Hob. XVII:6, may have been written in response to her death. Another friend in Vienna was Wolfgang Amadeus Mozart, whom Haydn met sometime around 1784. According to later testimony by Michael Kelly and others, the two composers occasionally played in string quartets together. Haydn was hugely impressed with Mozart's work and praised it unstintingly to others. Mozart evidently returned the esteem, as seen in his dedication of a set of six quartets, now called the "Haydn" quartets, to his friend.

In 1790, Prince Nikolaus died and was succeeded by a thoroughly unmusical prince who dismissed the entire musical establishment and put Haydn on a pension. Freed of his obligations, Haydn was able to accept a lucrative offer from Johann Peter Salomon, a German impresario, to visit England and conduct new symphonies with a large orchestra. The visit (1791–1792), along with a repeat visit (1794–1795), was a huge success. Audiences flocked to Haydn's concerts; Haydn augmented his fame and made large profits, thus becoming financially secure. Musically, the visits to England generated some of Haydn's best-known work, including the Surprise, Military, Drumroll, and London symphonies, the Rider quartet, and the "Gypsy Rondo" piano trio. The only misstep in the venture was an opera, Orfeo ed Euridice, also called L'Anima del Filosofo, which Haydn was contracted to compose, but whose performance was blocked by intrigues. Haydn made many new friends and was involved for a time in a romantic relationship with Rebecca Schroeter. Between visits, Haydn taught Ludwig van Beethoven. Beethoven found him unsatisfactory as a teacher and sought help from others; the relationship between the two was sometimes rather tense.

Haydn returned to Vienna in 1795, moved into a large house in the suburb of Gumpendorf, and turned to the composition of large religious works for chorus and orchestra. These include his two great oratorios (The Creation and The Seasons) and six masses for the Eszterházy family, which by this time was once again headed by a musically-inclined prince. Haydn also composed instrumental music: the popular Trumpet Concerto and the last nine in his long series of string quartets, including the Fifths, Emperor, and Sunrise quartets.

In 1802, an illness from which Haydn had been suffering for some time had increased in severity to the point that he became physically unable to compose. This was doubtless very difficult for him because, as he acknowledged, the flow of fresh musical ideas waiting to be worked out as compositions did not cease. Haydn was well cared for by his servants, and he received many visitors and public honours during his last years, but they could not have been very happy years for him. During his illness, Haydn often found solace by sitting at the piano and playing Gott erhalte Franz den Kaiser, which he had composed himself as a patriotic gesture in 1797. This melody later was used for the Austrian and German national anthems. Haydn died at the end of May in 1809, shortly after an attack on Vienna by the French army under Napoleon. He was 77. Among his last words was his attempt to calm and reassure his servants when cannon shot fell in the neighborhood. "My children, have no fear, for where Haydn is, no harm can fall." Two weeks later, a memorial service was held in the Schottenkirche on June 15, 1809, at which Mozart's Requiem was performed.