Oskar Cohn was a German lawyer, Zionist and socialist politician. He was a member of the German and Prussian parliament and the Weimar National Assembly representing the Social Democratic Party of Germany and the Independent Social Democratic Party of Germany.

The Weimar National Assembly, officially the German National Constitutional Assembly, was the popularly elected constitutional convention and de facto parliament of Germany from 6 February 1919 to 21 May 1920. As part of its duties as the interim government, it debated and reluctantly approved the Treaty of Versailles that codified the peace terms between Germany and the victorious Allies of World War I. The Assembly drew up and approved the Weimar Constitution that was in force from 1919 to 1933. With its work completed, the National Assembly was dissolved on 21 May 1920. Following the election of 6 June 1920, the new Reichstag met for the first time on 24 June 1920, taking the place of the Assembly.