Isaac Nachman Steinberg (Russian: Исаак Нахман Штейнберг; 13 July 1888 – 2 January 1957) was a lawyer, an Orthodox Jew, a Left Socialist-Revolutionary, politician, People's Commissar under Lenin, and a leader of the Jewish Territorialist movement and writer in Soviet Russia and in exile.

From December 10, 1917 to March 1918, he was People's Commissar (Narkom) of Justice in Vladimir Lenin's government during the Bolsheviks' short-lived coalition with the left wing of the SRs.

[2] On December 19, 1917, he signed an “Instruction” to the Revolutionary Tribunal on the termination of systematic repressions against individuals, institutions and the press and sent a corresponding telegram to the Soviets at all levels.

After the scandal caused by the murder of Andrei Ivanovich Shingarev and Fyodor Kokoshkin on the night of January 6–7, 1918, the Council of People's Commissars, after hearing the report of Steinberg, instructed the NKJ to “as soon as possible verify the thoroughness of the detention of political prisoners ... all those who cannot be charged within 48 hours should be released”.

During a meeting of the Council of People's Commissars in February, Lenin presented the draft of a decree, "The Socialist Fatherland in Danger!".

On March 19, as part of the southern delegation of the Left SR Central Committee, he went to Kursk to organize partisan detachments.

The League selected the Kimberley region of Western Australia as a place to purchase agricultural land where 75,000 Jewish refugees from Europe could be resettled.

In 1946, the Freeland League started negotiations with the Surinamese and Netherlands governments about the possible resettlement of 30,000 Jewish displaced persons from Europe in the Saramacca district of Surinam.

A delegation of the League headed by Steinberg, accompanied by Henri B. van Leeuwen and N. Fruchtbaum, visited Surinam in April 1947.

Steinberg was a prolific Yiddish writer, editor and prominent cultural activist, who played an important role in the development of the Yiddishist movement.

[8] Steinberg was an Orthodox Jew; it is rumored that during his short tenure as Commissar of Justice he refused to work on Sabbath, much to Lenin's dismay.

Russian Left Esers proposed a radically decentralized federation of worker syndicates, councils and cooperatives whose delegates are chosen by direct democracy and could be revoked at any moment.

He also noted, like some contemporary anarchists, that even an established syndicalist federation would not be completely free of elements or "crystals" of organized power.

According to Steinberg, even a relatively free and stateless social system has to acknowledge the existence of some reminiscent government-like structures within itself, in order to decentralize or dismantle them and further "anarchize" the society.

Steinberg viewed anarchism as an underlying principle, spirit, and drive of revolutionary socialism, rather than as a concrete political program with an ultimate goal.