Mieczysław Weinberg (also Moisey or Moishe Vainberg, Moisey Samuilovich Vaynberg; Russian: Моисей Самуилович Вайнберг; Polish: Mieczysław Wajnberg; December 8, 1919 in Warsaw – February 26, 1996 in Moscow) was a Soviet composer of Polish-Jewish origin. From 1939 he lived in the Soviet Union and Russia and lost most of his family in the Holocaust.

He left a large body of work that included twenty-two symphonies and seventeen string quartets; according to one reviewer he ranked as, "the third great Soviet composer, along with Prokofiev and Shostakovich".

Much confusion has been caused by different renditions of the composer's names. In the Polish language (i.e. prior to his move to the USSR), his name was spelled as 'Mieczysław Wajnberg' whereas in the Russian language (i.e. after the move) he was and still is known as 'Моисей Самуилович Вайнберг' (Moisey Samuilovich Vaynberg). In the world of Yiddish theater of antebellum Warsaw he was known as Moishe Weinberg (Yiddish: משה װײַנבערג), which is analogous to the Russian Moisey. Among close friends he would also go by his Polish diminutive 'Metek'. Re-transliteration of his surname from the Cyrillic alphabet (Вайнберг) back into the Latin alphabet produced a variety of spellings, including 'Weinberg', 'Vainberg', and 'Vaynberg'. The form 'Weinberg' is now being increasingly used as the most frequent English-language rendition of this common Jewish surname,notably in the latest edition of Grove and by Weinberg's biographer, Per Skans.

Weinberg was born in 1919 to a Jewish family in Warsaw. His father, Shmil (Szmuel or Samuil Moiseyevich) Weinberg (1882–1943, Russian), a well-known conductor and composer of the Yiddish theater, moved to Warsaw from Kishinev in 1916 and worked as a violinist and conductor for the Yiddish theatre Scala in Warsaw, where the future composer joined him as pianist at the age of 10 and later as a musical director of several performances. His mother, Sonia Wajnberg (née Karl, 1888–1943), was an actress in several Yiddish theater companies in Warsaw and Lodz. The family had already been the victim of anti-semitic violence in Bessarabia— some members of his family were killed during the Kishinev pogrom. One of composer's cousins (a son of his father's sister Khaya Vaynberg) - Isay Abramovich Mishne - was the secretary of the Military Revolutionary Committee of the Baku Soviet commune and was executed in 1918 along with the other 26 Baku Commissars.

Weinberg entered the Warsaw Conservatory, studying piano, at the age of twelve, and graduated in 1939. Two works (his first string quartet and a berceuse for piano) were composed before he fled to the Soviet Union at the outbreak of war. His parents and sister Esther remained behind, were interned at the Lodz ghetto and perished in the Trawniki concentration camp. He settled in Minsk, where he studied composition for the first time at the Conservatory there. At the outbreak of the World War II on the Soviet territory, Weinberg was evacuated to Tashkent (Central Asia), where he wrote works for the opera, as well as met and married Solomon Mikhoels' daughter Natalia Vovsi. There he also met Dmitry Shostakovich who was impressed by his talent and became his close friend. Meeting Shostakovich had a profound effect on the younger man, who said later that, "It was as if I had been born anew". In 1943 he moved to Moscow at Shostakovich's urging.

Weinberg's works were not banned during the Zhdanovshchina of 1948, but he was almost entirely ignored by the Soviet musical establishment; for a time he could make a living only by composing for the theatre and circus. In February 1953, he himself was arrested on charges of "Jewish bourgeois nationalism" in relation to the arrest of his father-in-law as a part of the so-called "Doctors' plot": Shostakovich wrote to Lavrenti Beria to intercede on Weinberg's behalf, as well as agreeing to look after Weinberg's daughter if his wife wеre also arrested. In the event, he was saved by Stalin's death the following month, and he was officially rehabilitated shortly afterwards.

Thereafter Weinberg continued to live in Moscow, composing and performing as a pianist. He and Shostakovich lived near to one another, sharing ideas on a daily basis. Besides the admiration which Shostakovich frequently expressed for Weinberg's works, they were taken up by some of Russia's foremost performers, including Emil Gilels, Leonid Kogan, Mstislav Rostropovich, Kurt Sanderling, and Kirill Kondrashin.

Towards the end of his life, Weinberg suffered from Crohn's disease and remained housebound for the last three years, although he continued to compose. He reportedly converted to Orthodox Christianity less than two months before his death (on January 3, 1996).

Ten years after his death a concert premiere of his opera The Passenger in Moscow sparked a posthumous revival. The British director David Pountney staged the opera at the 2010 Bregenz Festival and restaged it at English National Opera the following year, earning considerable acclaim while dividing critical opinion on the quality of the music and its suitability to the subject.

Weinberg's output includes twenty-two symphonies, other works for orchestra (including chamber symphonies and sinfoniettas), seventeen string quartets, eight violin sonatas (three solo and five with piano), twenty-four preludes for cello and six cello sonatas (two with piano and four solo), six piano sonatas, numerous other instrumental works, as well as more than 40 film and animation scores (including The Cranes are Flying, Palme d'Or at the Cannes Film Festival, 1958). He wrote seven operas, and considered one of them, The Passenger (Passazhirka) (written in 1967-68, premiered in 2006), to be his most important work. His piano quintet, piano trio and cello works have received performances in concert series and festivals across Europe and the USA in recent years, and the British record label Olympia has released over fifteen compact disc recordings of his music, consisting of both original recordings and remasterings of earlier Melodiya LPs.

Weinberg's works frequently have a strong programmatic element: throughout his life he continually referred back to his formative years in Warsaw and to the war which ended that earlier life. Typically, however, this darkness serves as a background to the finding of peace through catharsis. This desire for harmony is also evident in his musical style; Lyudmilla Nikitina emphasises the "neo-classical, rationalist clarity and proportion" of his works.

Although he never formally studied with Shostakovich, the older composer had an obvious influence on Weinberg's music. This is particularly noticeable in his 12th Symphony (1975–1976, Op.114)), which is dedicated to the composer's memory. Explicit connections include the pianissimo passage with celesta which ends the Fifth Symphony (1962, Op.76), reminiscent of Shostakovich's Fourth and written around the time of that work's premiere. Another Weinberg work, his sixth piano sonata (1960, Op.73), quotes one of the Shostakovich Preludes and Fugues. More general similarities in musical language include the use of extended melodies, repetitive themes and extreme registers. This has been one of the main criticisms voiced of Weinberg: Alexander Ivashkin has argued that composers such as Weinberg damaged not only their reputations, but also that of Shostakovich himself: "these works only served to kill off Shostakovich's music, to cover it over with a scab of numerous and bad copies".

Nevertheless, Shostakovich was not the only influence on Weinberg's style. Nikitina identifies Prokofiev, Myaskovsky, Bartók and Mahler as other influences, while the trumpet concerto quotes Mendelssohn's well-known Wedding March. Ethnic influences include not only Jewish music, but also Moldavian, Polish, Uzbek, and Armenian elements. Weinberg has been identified by some critics as the source of Shostakovich's own increased interest in Jewish themes.