Modern constitutionalism as an idea and practice is facing great uncertainty in current times. Scholarly debates focus predominantly on constitutions beyond the state, while the predicament of domestic constitutionalism is much less considered. This volume contributes to a theoretically informed analysis of the key challenges and changes affecting domestic constitutionalism in Europe and beyond, departing from the idea of ‘constitutional acceleration’ or the increased propensity of different actors to engage in (formal) reform of the constitutional order. The volume points to a fundamental change in the function of constitutions in that constitutions themselves are increasingly subjects of political contestation rather than framing political debates.The collection of essays addresses a range of critical challenges – including societal acceleration, depoliticization, civic engagement, multi-faceted constituent power, modernization, populism and nationalism, and transnationalization. The volume includes a variety of disciplinary, and in some cases interdisciplinary, approaches, including (political) sociology, political science, constitutional law, and constitutional and legal theory, and will be of interest to researchers and students in any of these areas. Case studies focus on the EU and the wider European context, and include highly relevant but little known or ill-understood cases, such as the recent constitutional events in Iceland, Italy, or Romania, and cases of democratic reversal, such as Hungary, while also engaging with traditional but rapidly changing cases of constitutional interest, such as the UK.