The Iron Front was an anti-Nazi, anti-monarchist, and anti-communist paramilitary organization formed in Germany on 16 December 1931 by the Social Democratic Party (SPD) with the Allgemeiner Deutscher Gewerkschaftsbund, the Reichsbanner and workers' sport clubs originally to counter the right-wing Harzburg Front formed by the National Socialist German Workers Party, the Stahlhelm and the German National People's Party. The organization sought to engage the old Reichsbanner, the SPD youth organization, and labor and liberal groups as a united front. The SPD rallied to the Iron Front, held mass demonstrations, fought fascists in the streets, and armed themselves. This is more than the SPD leaders wanted, but SPD workers grew increasingly revolutionary. In 1933, the organization was banned.

Die Eiserne Front war ein Zusammenschluss des Reichsbanners Schwarz-Rot-Gold, des Allgemeinen Deutschen Gewerkschaftsbundes (ADGB), des Allgemeinen freien Angestelltenbundes (Afa-Bund), der SPD und des Arbeiter Turn- und Sportbundes (ATSB) im Widerstand gegen den Nationalsozialismus.