Johannes Brahms (7 May 1833 – 3 April 1897), was a German composer and pianist, one of the leading musicians and a towering figure of the Romantic period. Born in Hamburg, Brahms spent much of his professional life in Vienna, Austria, where he was a leader of the musical scene. In his lifetime, Brahms's popularity and influence were considerable; following a comment by the nineteenth-century conductor Hans von Bülow, he is sometimes grouped with Johann Sebastian Bach and Ludwig van Beethoven as one of the Three Bs.

Brahms composed for piano, chamber ensembles, symphony orchestra, and for voice and chorus. A virtuoso pianist, he gave the first performance of many of his own works; he also worked with the leading performers of his time, including the pianist Clara Schumann and the violinist Joseph Joachim. Many of his works have become staples of the modern concert repertoire. Brahms, an uncompromising perfectionist, destroyed many of his works and left some of them unpublished. Brahms was at once a traditionalist and an innovator. His music is firmly rooted in the structures and compositional techniques of the Baroque and Classical masters. He was a master of counterpoint, the complex and highly disciplined method of composition for which Bach is famous, and also of development, a compositional ethos pioneered by Beethoven. Brahms aimed to honour the "purity" of these venerable "German" structures and advance them into a Romantic idiom, in the process creating bold new approaches to harmony and melody. While many contemporaries found his music too academic, his contribution and craftsmanship have been admired by subsequent figures as diverse as the progressive Arnold Schoenberg and the conservative Edward Elgar. The diligent, highly constructed nature of Brahms's works was a starting point and an inspiration for a generation of composers.

Brahms's father, Johann Jakob Brahms (1806–72), came to Hamburg from Dithmarschen, seeking a career as a town musician. He was proficient on several instruments, but found employment mostly playing the horn and double bass. In 1830, he married Johanna Henrika Christiane Nissen (1789–1865), a seamstress never previously married, who was seventeen years older than he was. Johannes Brahms had an older sister and a younger brother. Initially, they lived near the city docks, in the Gängeviertel quarter of Hamburg, for six months, before moving to a small house on the Dammtorwall, located on the northern perimeter of Hamburg, in the Inner Alster. Johann Jakob gave his son his first musical training. He studied piano from the age of seven with Otto Friedrich Willibald Cossel. For a time, Brahms also learned the cello. After his early piano lessons with Otto Cossel, Brahms studied piano with Eduard Marxsen, who had studied in Vienna with Ignaz von Seyfried (a pupil of Mozart) and Carl Maria von Bocklet (a close friend of Schubert). The young Brahms gave a few public concerts in Hamburg, but did not become well known as a pianist until he made a concert tour at the age of nineteen. (In later life, he frequently took part in the performance of his own works, whether as soloist, accompanist, or participant in chamber music.) He conducted choirs from his early teens, and became a proficient choral and orchestral conductor.

He began to compose quite early in life, but later destroyed most copies of his first works; for instance, Louise Japha, a fellow-pupil of Marxsen, reported a piano sonata that Brahms had played or improvised at the age of 11. His compositions did not receive public acclaim until he went on a concert tour as accompanist to the Hungarian violinist Eduard Reményi in April and May 1853. On this tour he met Joseph Joachim at Hanover, and went on to the Court of Weimar where he met Franz Liszt, Peter Cornelius, and Joachim Raff. According to several witnesses of Brahms's meeting with Liszt (at which Liszt performed Brahms's Scherzo, Op. 4, at sight), Reményi was offended by Brahms's failure to praise Liszt's Sonata in B minor wholeheartedly (Brahms supposedly fell asleep during a performance of the recently composed work), and they parted company shortly afterwards. Brahms later excused himself, saying that he could not help it, having been exhausted by his travels.

Joachim had given Brahms a letter of introduction to Robert Schumann, and after a walking tour in the Rhineland, Brahms took the train to Düsseldorf, and was welcomed into the Schumann family on arrival there. Schumann, amazed by the 20 year-old's talent, published an article entitled "Neue Bahnen" (New Paths) in the October 28, 1853 issue of the journal Neue Zeitschrift für Musik alerting the public to the young man, who, he claimed, was "destined to give ideal expression to the times." This pronouncement was received with some scepticism outside of Schumann's immediate circle, and may have increased Brahms's naturally self-critical need to perfect his works and technique. While he was in Düsseldorf, Brahms participated with Schumann and Albert Dietrich in writing a sonata for Joachim; this is known as the "F-A-E Sonata" (German: Frei aber einsam). He became very attached to Schumann's wife, the composer and pianist Clara, fourteen years his senior, with whom he would carry on a lifelong, emotionally passionate, but probably platonic, relationship. Brahms never married, despite strong feelings for several women and despite entering into an engagement, soon broken off, with Agathe von Siebold in Göttingen in 1859. After Schumann's attempted suicide and subsequent confinement in a mental sanatorium near Bonn in February 1854, Brahms was the main intercessor between Clara and her husband, and found himself virtually head of the household.

After Schumann's death at the sanatorium in 1856, Brahms divided his time between Hamburg, where he formed and conducted a ladies' choir, and the principality of Detmold, where he was court music-teacher and conductor. He was the soloist at the premiere of his Piano Concerto No. 1 in 1859. He first visited Vienna in 1862, staying there over the winter, and, in 1863, was appointed conductor of the Vienna Singakademie. Though he resigned the position the following year, and entertained the idea of taking up conducting posts elsewhere, he based himself increasingly in Vienna and soon made his home there. From 1872 to 1875, he was director of the concerts of the Vienna Gesellschaft der Musikfreunde; afterwards, he accepted no formal position. He declined an honorary doctorate of music from University of Cambridge in 1877, but accepted one from the University of Breslau in 1879, and composed the Academic Festival Overture as a gesture of appreciation.

He had been composing steadily throughout the 1850s and 60s, but his music had evoked divided critical responses, and the Piano Concerto No. 1 had been badly received in some of its early performances. His works were labelled old-fashioned by the 'New German School' whose principal figures included Liszt and Richard Wagner. Brahms admired some of Wagner's music and admired Liszt as a great pianist, but the conflict between the two schools, known as the War of the Romantics, soon embroiled all of musical Europe. In the Brahms camp were his close friends: Clara Schumann, the influential music critic Eduard Hanslick, and the leading Viennese surgeon Theodor Billroth. In 1860, Brahms attempted to organize a public protest against some of the wilder excesses of the Wagnerians' music. This took the form of a manifesto, written by Brahms and Joachim jointly. The manifesto, which was published prematurely with only three supporting signatures, was a failure, and he never engaged in public polemics again.

It was the premiere of A German Requiem, his largest choral work, in Bremen, in 1868, that confirmed Brahms's European reputation and led many to accept that he had conquered Beethoven and the symphony. This may have given him the confidence finally to complete a number of works that he had wrestled with over many years, such as the cantata Rinaldo, his first string quartet, third piano quartet, and most notably his first symphony. This appeared in 1876, though it had been begun (and a version of the first movement seen by some of his friends) in the early 1860s. The other three symphonies then followed in 1877, 1883, and 1885. From 1881, he was able to try out his new orchestral works with the court orchestra of the Duke of Meiningen, whose conductor was Hans von Bülow. He was the soloist at the premiere of his Piano Concerto No. 2 in 1881.

Brahms frequently travelled, both for business (concert tours) and pleasure. From 1878 onwards, he often visited Italy in the springtime, and he usually sought out a pleasant rural location in which to compose during the summer. He was a great walker and especially enjoyed spending time in the open air, where he felt that he could think more clearly.

In 1889, one Theo Wangemann, a representative of American inventor Thomas Edison, visited the composer in Vienna and invited him to make an experimental recording. Brahms played an abbreviated version of his first Hungarian dance on the piano. The recording was later issued on an LP of early piano performances (compiled by Gregor Benko). Although the spoken introduction to the short piece of music is quite clear, the piano playing is largely inaudible due to heavy surface noise. Nevertheless, this remains the earliest recording made by a major composer. Analysts and scholars remain divided, however, as to whether the voice that introduces the piece is that of Wangemann or of Brahms.

In 1889, Brahms was named an honorary citizen of Hamburg, until 1948 the only one born in Hamburg.

In 1890, the 57 year-old Brahms resolved to give up composing. However, as it turned out, he was unable to abide by his decision, and in the years before his death he produced a number of acknowledged masterpieces. His admiration for Richard Mühlfeld, clarinetist with the Meiningen orchestra, moved him to compose the Clarinet Trio, Op. 114, Clarinet Quintet, Op. 115 (1891), and the two Clarinet Sonatas, Op. 120 (1894). He also wrote several cycles of piano pieces, Opp. 116–119, the Four Serious Songs (Vier ernste Gesänge), Op. 121 (1896), and the Eleven Chorale Preludes for organ, Op. 122 (1896).

While completing the Op. 121 songs, Brahms developed cancer (sources differ on whether this was of the liver or pancreas). His condition gradually worsened and he died on April 3, 1897. Brahms is buried in the Zentralfriedhof in Vienna.