The central thesis of this paper is that political antisemitism cannot be understood without taking into account what should be regarded as its Christian foundation proper, the perception and stigmatization of Jews as dangerous aliens. By introducing the differentiation between an ‘chimerical anti-Semitism’, a product of the pre-modern mental set-up, often generated by Christian religious phantasmagoria, and a modern anti-Semitism with concrete references to social relations in industrial and post-industrial societies with a trend to associate exclusively Jews to societal ills, it is argued that the latter can be regarded as an ideological construction which represent the rationalization of deeply inbred preconceptions about Jews as radical aliens and as bearers of a set of negative characteristics. The article presents a reflection on the Christian origins, the development of Jew-hatred during the Middle Ages and the early modern period and discusses the extension of secularized anti-Semitic conceptions in various European societies as well as the main observable topical patterns of judeophobia in modern times. Three forms of exclusion can be identified: the exclusion of Jews from emergent national communities during the nation building process as ‘national aliens’ of an extreme sort; racist anti-Semitism, based on the phantasm of Jews as ‘racial aliens’ and grounded in the idea of the racial division of humanity; and a picture of the Jews as a monstrous – because consciously hidden – other as an reaction to the process Jewish ‘assimilation’. The paper comes to the conclusion that concrete references to social relations and social functions of judeophobia do not suffice to explain it in a satisfactory manner. This cannot be accomplished without reference to the discussed Christian historical foundations.