Adolph Abramovich Joffe (Russian: Адо́льф Абра́мович Ио́ффе; alternatively transliterated as Adolf Ioffe or Yoffe; 10 October 1883 – 16 November 1927) was a Russian revolutionary, Bolshevik politician and Soviet diplomat of Karaite descent.

Adolf Abramovich Joffe was born in Simferopol, Crimea, Russian Empire, in a wealthy Karaite family. He became a social democrat in 1900 while still in high school, formally joining the Russian Social Democratic Labor Party in 1903. In 1904 Joffe was sent to Baku, which he had to flee to avoid arrest. He was then sent to Moscow, but had to flee again, this time abroad. After the events of Bloody Sunday on 9 January 1905, Joffe returned to Russia and took an active part in the Russian Revolution of 1905. In early 1906 he was forced to emigrate and lived in Berlin until his expulsion from Germany in May 1906.

In Russia, Joffe was close to the Menshevik faction within the Russian Social Democratic Party. However, after moving to Vienna in May 1906, he became close to Leon Trotsky's position and helped Trotsky edit Pravda from 1908 to 1912 while studying medicine and psychoanalysis with Alfred Adler. He also used his family's fortune to support Pravda financially. During the course of his underground revolutionary activity Joffe adopted the party name "V. Krymsky," the surname meaning "The Crimean."

In 1912 Joffe was arrested while visiting Odessa, imprisoned for 10 months and then exiled to Siberia.

In 1917, Joffe, freed from the Siberian exile by the February Revolution, returned to the Crimea. Crimean social democrats sent him to the capital, Petrograd, to represent them, but he soon moved to an internationalist revolutionary position, which made it impossible for him to remain in an organization dominated by less radical Mensheviks. Instead, he joined forces with Trotsky, who had just returned from abroad.

In May 1917, Joffe and Trotsky temporarily joined Mezhraiontsy who merged with the Bolsheviks at the VI Bolshevik Party Congress held between 26 July and 3 August 1917 (all dates are Old Style until February 1918). At the Congress, Joffe was elected a candidate (non-voting) member of the Central Committee, but two days later, on 5 August, the Central Committee, some of whose members were in prison, in hiding or lived far from Petrograd and could not attend its meetings, made Joffe a member of its permanent ("narrow") bureau. On 6 August Joffe was made an alternate member of the Central Committee Secretariat and on 20 August made a member of the editorial board of the Bolshevik newspaper Pravda which was then temporarily called Proletary (Proletarian) for legal reasons.

Joffe headed the Bolshevik faction in the Petrograd Duma (city government) in the fall of 1917 and was one of the Duma's delegates to the Democratic Conference between 14 and 22 September. Although Joffe, along with Lenin and Trotsky, opposed the Bolsheviks' participation in the consultative Pre-parliament created by the Democratic Conference, the motion was carried by the majority of Bolshevik deputies at the Democratic Conference and Joffe was made a Bolshevik member of the Pre-parliament. Two weeks later, on 7 October, once the more radical Bolshevik faction gained the upper hand, Joffe and other Bolsheviks walked out of the Pre-parliament.

In October 1917, Joffe supported Lenin's and Trotsky's revolutionary position against Grigory Zinoviev's and Lev Kamenev's more moderate position, demanding that the latter be expelled from the Central Committee after an apparent breach of party discipline. Joffe served as the Chairman of the Petrograd Military Revolutionary Committee which overthrew the Russian Provisional Government on 25–26 October 1917. Immediately after the revolution, he supported Lenin and Trotsky against Zinoviev, Kamenev, Alexei Rykov and other Bolshevik Central Committee members who would have shared power with other socialist parties.^{[clarification needed]}