Gerhart Eisler was a German politician, editor and journalist. Along with his sister Ruth Fischer, he was a very early member of the Austrian German Communist Party (KPDÖ) and then a prominent member of the Communist Party of Germany during the Weimar Republic.

Ruth Fischer was an Austrian and German Communist, and a co-founder of the Austrian Communist Party (KPÖ) in 1918. Along with her partner Arkadi Maslow, she led the Communist Party of Germany (KPD) through both the May 1924 and December 1924 federal elections. After being removed from the KPD, she became involved with various anti-Stalinist left-wing groups, and would remain a staunch anti-Stalinist activist for the rest of her life.