Karl Erich Rudolf Formis (25 December 1894 - 23 January 1935) was a German engineer and radio engineer at the Süddeutsche Rundfunk AG (SÜRAG) subsidiary of Reichs-Rundfunk-Gesellschaft. Formis was a pioneer of the German amateur radio movement. During the period of Nazi rule in Germany, he transmitted anti-Nazi radio broadcasts from Czechoslovakia for the Black Front organisation, using a self-built shortwave radio. Formis was murdered by the Sicherheitsdienst on the orders of Reinhard Heydrich.