Iwan Katz (1 February 1889 - 20 September 1956) was a German politician (SPD, USPD, KPD, AAUE, SED and UAPD). In many ways the period of his greatest influence, within the Communist Party and after his expulsion from it in 1926 outside it, came between 1924 and approximately 1927. Between 1924 and 1928 he served as a member of parliament (Reichstags Mitglied). On account of his record of activism he was subject to persecution during the twelve Hitler years, spending the years from 1941 till 1944 in concentration camps. He nevertheless survived became a post-war force in the politics both of Berlin and, till serious heart triggered disease his retirement in 1954, in East and West Germany more broadly.