While scholars within the English School have increasingly approached the traditionally liberal concept of solidarism in a normatively agnostic fashion, the idea of an ‘illiberal solidarism’ and historical manifestations thereof remain underexplored. One notable case in point surrounds the peculiar body of Italian interwar international thought, herein referred to as ‘international Fascism’. By discerning a synchronic outline of international Fascism, alongside the manner by which this project mutated and ultimately failed as it transformed from a vision theorised in the abstract to a practical initiative under the auspices of the Fascist regime, this article offers historical and theoretical insights into the realisability of illiberal forms of solidarism. Combining this historical account with theoretical insights derived from Reus-Smit's study on international order under conditions of cultural diversity, this article argues that the realisation of some form of solidarism necessitates the acceptance of a substantive pluralist component. Yet messianic illiberal visions that endeavour to retain the states-system, while simultaneously asserting the superiority of one community or a highly exclusionary vision of the ‘good life’, ostensibly lack the capacity to reconcile the contradictions inherent in efforts to universalise such projects.