Maxim Maksimovich Litvinov (ru: Макси́м Макси́мович Литви́нов) (July 17, 1876–December 31, 1951) was a Russian revolutionary and prominent Soviet diplomat.

Born Meir Genoch Mojsiejewicz Wallach-Finkelstein (simplified into Max Wallach, Макс Ва́ллах) into a wealthy Jewish banking family in Białystok in Congress Poland, he joined the Russian Social Democratic Labour Party in 1898. The party was an illegal organization, and it was customary to use pseudonyms. He changed his name to Maxim Litvinov, but was also known as Papasha and Maksimovich. His early responsibilities included carrying propaganda work in Chernigiv region. In 1900 Litvinov became a member of Kiev party committee, but the entire committee was arrested in 1901. After 18 months of captivity, he led an escape of 11 inmates from Lukyanovskaya prison and lived in exile in Switzerland, where he was an editor for the revolutionary newspaper Iskra.

In 1903, he joined the Bolshevik faction and returned to Russia. After the 1905 Revolution he became editor of the SDLP's first legal newspaper, Novaya Zhizn' (New Life) in Petrograd.

When the Russian government began arresting Bolsheviks in 1906, Litvinov left the country and spent the next ten years living in London, where he was active in the International Socialist Bureau. There he met and married the impulsive, free-spirited Ivy Low .

After the October Revolution of 1917, Litvinov was appointed by Vladimir Lenin as the Soviet government's representative in Britain. However, in 1918, Litvinov was arrested by the British government and held hostage until exchanged for Bruce Lockhart , a British diplomat who had been imprisoned in Russia.

Litvinov was then employed as the Soviet government's roaming ambassador. It was largely through his efforts that Britain agreed to end its economic blockade of the Soviet Union. Litvinov also negotiated several trade agreements with European countries.

In 1930, Joseph Stalin appointed Litvinov as Narkom (Minister) of Foreign Affairs. A firm believer in collective security, Litvinov worked very hard to form a closer relationship with France and Britain. In 1933 he successfully persuaded the United States to officially recognize the Soviet government. Franklin D. Roosevelt sent comedian Harpo Marx to the Soviet Union as a good-will amabassador, and Litvinov and Marx became friends and even performed a routine on stage together. Litvinov also actively facilitated the acceptance of the USSR into the League of Nations where he represented his country in 1934—1938.

In early May 1939, because of his Jewish origins, as well as his role in helping to build an international Popular Front against German and Italian fascism and in building ties with the Western powers in order to contain German power, Litvinov was replaced as foreign minister in order to facilitate negotiations leading up to the Non-Aggression Pact with Germany, which was signed by Litvinov's successor, Vyacheslav Molotov, in August of that year.

After the outbreak of the Great Patriotic War in June 1941, Joseph Stalin appointed Litvinov as Deputy Commissar of Foreign Affairs. He also served as Ambassador to the United States from 1941 to 1943 and significantly contributed to lend lease agreement signed in 1942.

Perhaps more than anyone else, the businesslike diplomat helped to bring the Soviet Union out of its post-revolutionary isolation; however, Litvinov bluntly condemned Stalin's policies during and after the war with Germany.