Leoš Janáček, son of schoolmaster Jiří (1815 – 1866), and Amalie, (née Grulich) Janáček (1819 – 1884), was born in Hukvaldy, Moravia, (then part of the Austrian Empire). He was a gifted child in a family of limited means, and showed an early musical talent in choral singing. His father wanted him to follow the family tradition, and become a teacher, but deferred to Janáček's obvious musical abilities. In 1865 young Janáček enrolled as a ward of the foundation of the Abbey of St. Thomas in Brno, where he took part in choral singing under Pavel Křížkovský and occasionally played the organ. One of his classmates, František Neumann, later described Janáček as an "excellent pianist, who played Beethoven symphonies perfectly in a piano duet with a classmate, under Křížkovský's supervision". Křížkovský found him a problematic and wayward student but recommended his entry to the Prague Organ School. Janáček later remembered Křížkovský as a great conductor and teacher.

Janáček originally intended to study piano and organ but eventually devoted himself to composition. He wrote his first vocal compositions while choirmaster of the Svatopluk Artisan's Association (1873 – 76). In 1874 he enrolled at the Prague organ school, under František Skuherský and František Blažek. His student days in Prague were impoverished; with no piano in his room, he had to make do with a keyboard drawn on his tabletop. His criticism of Skuherský's performance of the Gregorian mass was published in the March 1875 edition of the journal Cecilie and led to his expulsion from the school - but Skuherský relented, and on 24 July 1875 Janáček graduated with the best results in his class. On his return to Brno he earned a living as a music teacher, and conducted various amateur choirs. From 1876 he taught music at Brno's Teachers Institute. Among his pupils there was Zdenka Schulzová, daughter of Emilian Schulz, the Institute director. She was later to be Janáček's wife. In 1876 he also became a piano student of Amálie Wickenhauserová - Nerudová, with whom he co-organized chamber concertos and performed in concerts over the next two years. In February, 1876, he was voted choirmaster of the Beseda brněnská Philharmonic Society. Apart from an interruption from 1879 to 1881, he remained its choirmaster and conductor until 1888.

From October 1879 to February 1880 he studied piano, organ, and composition at the Leipzig Conservatory. While there, he composed Thema con variazioni for piano in B flat, subtitled Zdenka's Variations. Dissatisfied with his teachers (among them Oskar Paul and Leo Grill), and denied a studentship with Saint-Saëns in Paris, Janáček moved on to the Vienna Conservatory where from April to June 1880 he studied composition with Franz Krenn. He concealed his opposition to Krenn's neo-romanticism, but he quit Joseph Dachs's classes and further piano study when he was criticised for his piano style and technique. He submitted a violin sonata (now lost) to a Vienna Conservatory competition, but the judges rejected it as "too academic". Janáček left the conservatory in June, 1880, disappointed despite Franz Krenn's very complimentary personal report. He returned to Brno where on 13 July 1881, he married his young pupil Zdenka Schulzová.

Janáček was appointed director of the organ school, and held this post until 1919, when the school became the Brno Conservatory. In the mid 1880s Janáček began composing more systematically. Among other works, he created the Four male voice choruses (1886), dedicated to Antonín Dvořák, and his first opera, Šárka (1887 - 8). During this period he began to collect and study folk music, songs and dances. In the early months of 1887 he sharply criticized the comic opera The Bridegrooms, by Czech composer Karel Kovařovic, in a Hudební listy journal review: "Which melody stuck in your mind? Which motif? Is this dramatic opera? No, I would write on the poster: "Comedy performed together with music", since the music and the libretto aren't connected to each other". Janáček's review apparently led to mutual dislike and later professional difficulties when Kovařovic, as director of the National Theatre in Prague, refused to stage Janáček's opera Jenůfa.

From the early 1890s, Janáček led the mainstream of folklorist activity in Moravia and Silesia, using a repertoire of folksongs and dances in orchestral and piano arrangements. Most of his achievements in this field were published in 1899 - 1901 though his interest in folklore would be lifelong. His compositional work was still influenced by the declamatory, dramatic style of Smetana and Dvořák. He expressed very negative opinions on German neo-classicism and especially on Wagner in the Hudební listy journal, which he founded in 1884. The death of his second child, Vladimír, in 1890 was followed by an attempted opera, Beginning of the Romance (1891) and the cantata Amarus(1897).

In the first decade of the 20th century Janáček composed choral church music including Otčenáš (Our Father, 1901), Constitutes (1903) and Ave Maria (1904). In 1901 the first part of his piano cycle On an Overgrown Path was published, and gradually became one of his most frequently performed works. In 1902 Janáček visited Russia twice. On the first occasion he took his daughter Olga to St.Petersburg, where she stayed to study Russian. Only three months later, he returned to St. Petersburg with his wife because Olga was very ill. They took her back to Brno, but her health was worsening. Janáček expressed his painful feelings for his daughter in a new work, his opera Jenůfa, in which the suffering of his daughter became Jenůfa's. When Olga died in February 1903, Janáček dedicated Jenůfa to her memory. The opera was performed in Brno in 1904, with reasonable success, but Janáček felt this was no more than a provincial achievement. He aspired to recognition by the more influential Prague opera, but Jenůfa was refused there (twelve years passed before its first performance in Prague). Dejected and emotionally exhausted, Janáček went to Luhačovice spa to recover. There he met Kamila Urválková, whose love story supplied the theme for his next opera, Osud (Destiny).

In 1905 Janáček attended a demonstration in support of a Czech university in Brno, where the violent death of František Pavlík (a young joiner) at the hands of the police inspired his 1. X. 1905 piano sonata. The incident led him to further promote the anti-German and anti-Austrian ethos of the Russian Circle, which he had co-founded in 1897 and which would be officially banned by the Austrian police in 1915. In 1906 he approached the Czech poet Petr Bezruč, with whom he later collaborated, composing several choral works based on Bezruč's poetry. These included Kantor Halfar (1906), Maryčka Magdónova (1908), and Sedmdesát tisíc (1909). Janáček's life in the first decade of the 20th century was complicated by personal and professional difficulties. He still yearned for artistic recognition from Prague. He destroyed some of his works - others remained unfinished. Nevertheless, he continued composing, and would create several remarkable choral, chamber, orchestral and operatic works, the most notable being the 1914 Cantata Věčné evangelium (The Eternal Gospel), Pohádka (Fairy tale) for violoncello and piano (1910), the 1912 piano cycle V mlhách (In the Mist) and his first symphonic poem Šumařovo dítě (A Fiddler's Child). His fifth opera, Výlet pana Broučka do měsíce, composed from 1908 to 1917, has been characterized as the most "purely Czech in subject and treatment" of all Janáček's operas.

In 1916 he started what would be a long professional and personal relationship with theatre critic, dramatist and translator Max Brod. In the same year Jenůfa, revised by Kovařovic, was finally accepted by the National Theatre; its performance in Prague (1916) was a great success, and brought Janáček his first acclaim. He was 62. Following the Prague première, he began a relationship with singer Gabriela Horváthová, which led to his wife Zdenka's attempted suicide and their "informal" divorce. A year later (1917) he met Kamila Stösslová, a young married woman 38 years his junior, who was to inspire him for the remaining years of his life. He conducted an obsessive and (on his side at least), passionate correspondence with her, of nearly 730 letters. From 1917 to 1919, deeply inspired by Stösslová, he composed The Diary of One Who Disappeared. As he completed its final revision, he began his next 'Kamila' work, the opera Káťa Kabanová.

In 1920 Janáček retired from his post as director of the Brno Conservatory, but continued to teach until 1925. In 1922 he attended a lecture by the Indian philosopher - poet Rabindranath Tagore, and used a Tagore poem as the basis for the chorus The Wandering Madman. Later that year he encountered the microtonal works of Alois Hába. In the early 1920s Janáček completed his opera The Cunning Little Vixen, which had been inspired by a serialized novella in the newspaper Lidové noviny.

In Janáček's 70th year (1924) his biography was published by Max Brod, and he was interviewed by Olin Downes for the New York Times. In 1925 he retired from teaching, but continued composing and was awarded the first honorary doctorate to be given by Masaryk University in Brno. In the spring of 1926 he created the monumental orchestral work Sinfonietta, which rapidly gained wide critical acclaim. In the same year he went to England at the invitation of Rosa Newmarch. A number of his works were performed in London, including his first string quartet, the wind sextet Youth, and his violin sonata. Shortly after, and still in 1926, he started to compose a setting to an Old Church Slavonic text. The result was the large scale orchestral Glagolitic Mass. Janáček was an atheist, and critical of the organised Church, but religious themes appear frequently in his work. The Glagolitic Mass was partly inspired by the suggestion by a clerical friend, and partly by Janáček's wish to celebrate the anniversary of Czechoslovak independence. In 1927 - the year of Sinfonietta's first performances in New York, Berlin and Brno - he began to compose his final operatic work, From the House of the Dead, the third Act of which was found on his desk after his death. In January 1928 he began his second string quartet, the "Intimate Letters", his "manifesto on love". Meanwhile, Sinfonietta was performed in London, Vienna and Dresden. In his later years, the still active Janáček became an international celebrity. He became a member of the Prussian Academy of Arts in Berlin in 1927, along with Arnold Schönberg and Paul Hindemith. His operas and other works were finally performed at the world stages, though From the House of the Dead was first performed posthumously. In August 1928 he took an excursion to Štramberk with Kamila Stösslová and her son Otto, but caught a chill, which developed into pneumonia. He died on the 12th August 1928 in Ostrava, at the sanatorium of Dr. L. Klein. He was given a large public funeral, to music from the last scene of his Cunning Little Vixen, and was buried in the Field of Honour at the Central Cemetery, Brno.

Janáček's life was filled by work. He led the organ school, was a Professor at the teachers institute and gymnasium in Brno, collected his "speech tunes" and was composing. From an early age he presented himself as an individualist and his firmly formulated opinions often led to conflict. He unhesitatingly criticized his teachers, who considered him a defiant and anti authoritarian student. His own students found him strict and uncompromising. Vilém Tauský, one of his pupils, described his encounters with Janáček as somewhat distressing for someone unused to his personality, and noted that Janáček's characteristically staccato speech rhythms were reproduced in some of his operatic characters. In 1881, Janáček gave up his leading role with the Beseda brněnská, as a response to criticism, but a rapid decline in "Beseda"'s performance quality led to his recall in 1882.

His married life, settled and calm in its early years, became increasingly tense and difficult following the death of his daughter, Olga. Years of effort in obscurity took their toll, and almost ended his ambitions as a composer.: "I was beaten down", he wrote later; "my own students gave me advices, how to compose, how to speak through orchestra". Success in 1916 - when Karel Kovařovic finally decided to perform Jenůfa in Prague - brought its own problems. Janáček grudgingly resigned himself to the changes forced upon his work. Its success brought him into Prague's music scene and the attentions of soprano Gabriela Horvátová, who guided him through Prague society. Janáček was enchanted by her. On his return to Brno, he appears not to have concealed his new passion from Zdenka, who responded by attempting suicide. Janáček was furious with Zdenka and tried to instigate a divorce, but lost interest in Horvátová. Zdenka, anxious to avoid the public scandal of formal divorce, persuaded him to settle for an "informal" divorce. From then on, until Janáček's death, they would live separate lives in the same household.

In 1917 he began his lifelong, inspirational and unrequited passion for Kamila Stösslová, who neither sought nor rejected his devotion. Janáček pleaded for first name terms in their correspondence. In 1927 she finally agreed and signed herself "Tvá Kamila" (Your Kamila) in a letter, which Zdenka found. This revelation provoked a furious quarrel between Zdenka and Janáček, though their living arrangements did not change - Janáček seems to have persuaded her to stay. In 1928, the year of his death, Janáček confessed his intention to publicise his feelings for Stösslová. Max Brod had to dissuade him. Janáček's contemporaries and collaborators described him as mistrustful and reserved, but capable of obsessive passion for those he loved. His overwhelming passion for Stösslová was sincere but verged upon self-destruction. Their letters remain an important source for Janáček's artistic intentions and inspiration. His letters to his long suffering wife are, by contrast, mundanely descriptive. Zdenka seems to have destroyed all hers to Janáček. Only a few postcards survive.

In 1874 Janáček became friends with Antonín Dvořák, and began composing in a relatively traditional romantic style. After his opera Šárka (1887 – 1888), his style absorbed elements of Moravian and Slovak folk music.

His musical assimilation of the rhythm, pitch contour and inflections of normal Czech speech helped create the very distinctive vocal melodies of his opera Jenůfa (1904), whose 1916 success in Prague was to be the turning point in his career. In Jenůfa, Janáček developed and applied the concept of "speech tunes" to build a unique musical and dramatic style quite independent of "Wagnerian" dramatic method. He studied the circumstances in which "speech tunes" changed, the psychology and temperament of speakers and the coherence within speech, all of which helped render the dramatically truthful roles of his mature operas, and became one of the most significant markers of his style. Janáček took these stylistic principles much farther in his vocal writing than Modest Mussorgsky, and thus anticipates the later work of Béla Bartók. The stylistic basis for his later works originates in the period of 1904 - 1918, but Janáček composed the majority of his output - and his best known works - in the last decade of his life.

Much of Janáček's work displays great originality and individuality. It employs a vastly expanded view of tonality, uses unorthodox chord spacings and structures, and often, modality: "there is no music without key. Atonality abolishes definite key, and thus tonal modulation.... Folksong knows of no atonality." Janáček features accompaniment figures and patterns, with (according to Jim Samson) "the on-going movement of his music... similarly achieved by unorthodox means; often a discourse of short, 'unfinished' phrases comprising constant repetitions of short motifs which gather momentum in a cumulative manner." Janáček named these motifs "sčasovka" in his theoretical works. "Sčasovka" has no strict English equivalent, but John Tyrrell, a leading specialist on Janáček's music, describes it as "a little flash of time, almost a kind of musical capsule, which Janáček often used in slow music as tiny swift motifs with remarkably characteristic rhythms that are supposed to pepper the musical flow." Janáček's use of these repeated motifs demonstrates a remote similarity to minimalist composers (Sir Charles Mackerras called Janáček "the first minimalist composer").

Janáček belongs to a wave of 20th century composers who sought greater realism and greater connection with everyday life, combined with a more all encompassing use of musical resources. His operas in particular demonstrate the use of "speech" - derived melodic lines, folk and traditional material, and complex modal musical argument. Janáček's works are still regularly performed around the world, and are generally considered popular with audiences. He would also inspire later composers in his homeland, as well as music theorists, among them Jaroslav Volek, to place modal development alongside harmony of importance in music.

The operas of his mature period, Jenůfa (1904), Káťa Kabanová (1921), The Cunning Little Vixen (1924), The Makropulos Affair (1926) and From the House of the Dead (after a novel by Dostoyevsky and premiered posthumously in 1930) are considered his finest works. The Australian conductor Sir Charles Mackerras has become particularly closely associated with them.

His chamber music, while not especially voluminous, includes works which are generally considered to be "in the standard repertory" as 20th century classics, particularly his two string quartets: Quartet No. 1, "The Kreutzer Sonata" inspired by the Tolstoy novel, and the Quartet No. 2, "Intimate Letters". Milan Kundera called these compositions the peak of Janáček's output.

At the Frankfurt am Main Festival of Modern Music in 1927 Ilona Štěpánová-Kurzová performed the world premiere of Janáček's lyrical Concertino for piano, two violins, viola, clarinet, French horn and bassoon; the Czech premiere took place in Brno on February 16, 1926. A comparable chamber work for an even more unusual set of instruments, the Capriccio for piano left hand, flute, two trumpets, three trombones and tenor tuba, was written for pianist Otakar Hollmann, who lost the use of his right hand during World War I. After its premiere in Prague on March 2, 1928, it gained considerable acclaim in the musical world.

Other well known pieces by Janáček include the Sinfonietta, the Glagolitic Mass (the text written in Old Church Slavonic), and the rhapsody Taras Bulba. These pieces and the above mentioned five late operas were all written in the last decade of Janáček's life.

Janáček established a school of composition in Brno. Among his notable pupils were Jan Kunc, Václav Kaprál, Vilém Petrželka, Jaroslav Kvapil, Osvald Chlubna, Břetislav Bakala, and Pavel Haas. Most of his students neither imitated nor developed Janáček's style, which left him no direct stylistic descendants. According to Milan Kundera, Janáček developed a personal, modern style in relative isolation from contemporary modernist movements but was in close contact with developments in modern European music. His path towards the innovative "modernism" of his later years was long and solitary, and he achieved true individuation as a composer around his 50th year.