However, the rise of populism may be more complex and ambiguous for GC than its authoritarian and nationalist incarnations suggest. Hence, ‘from the global constitutionalist perspective Trumpism represents an attack on the three foundational features of the global constitution – democracy, human rights, and the rule of law’ (Havercroft et al. Recent editorials of this journal worried that ‘far right populist authoritarian parties and leaders enjoying considerable successes across Europe and the US decay of ‘the West’ anchoring a normative model of global order in which commitments to human rights, democracy and the rule of law are central’ (Kumm et al. The contemporary rise of populism appears like an existential threat to Global Constitutionalism (GC), as politicians like Donald Trump or Matteo Salvini routinely ignore, discredit or actively undermine normative principles underlying global politics. The populist spectre haunting Global Constitutionalism These findings suggest an emerging politicisation of the process of global constitutionalisation at the societal level according to principles of democratic legitimacy and global constitutional differentiation depending on outcomes of these normatively ambivalent and empirically contingent political contests. Further, neo-socialist populists campaign against neoliberal principles in GC, but remain divided about supporting political principles beyond the state. While all cases contest a perceived lack of popular sovereignty in a largely non-majoritarian global constitutional order, varieties of populism present contrasting responses: communitarian types push for global de-constitutionalisation in line with illiberal nationalist majoritarianism, while cosmopolitan types support global constitutionalisation according to liberal and democratic principles. Illustrative case studies of the Alternative for Germany, the Polish Law and Justice Party, the Democracy in Europe Movement and Peru’s Alberto Fujimori substantiate these empirically. Building on the ideational approach to populism and a framework of transnational politicisation, a proposed typology identifies both communitarian types of populism and cosmopolitan types of populism. It shows that populist contestation is more ambivalent than often suggested: its challenge depends on the populist variety and can both undermine or support liberal principles of GC. This article analyses the rise of populism and its discursive challenge to global constitutionalism (GC).