This special issue examines conspiracist antisemitic print culture in the Nordic countries from the Bolshevik Revolution of 1917 to the defeat of Nazi Germany in 1945. To contrast the universal patterns and particularities of the cases of Finland, Sweden, Denmark and Norway, the issue includes two contributions analysing Spain and Britain. Together, the articles provide empirical in-depth knowledge of the character and dissemination of conspiracist antisemitism in a particular time and within a particular region. Our aim is to expand the general knowledge of conspiracism as a historical phenomenon through the prism of antisemitism. In the introduction, we present the conditions of historical antisemitism in each case study as well as the conceptual framework of this issue, focusing on terms such as conspiracism, conspiracy and conspiracy theories. We argue that antisemitism can be interpreted as a longue-durée conspiracist tradition, marked by a dialectic interaction between continuity and dynamic changes.