The concept of 'architectures' of global governance is a useful heuristic device to help understand the macro level of institutions and governance mechanisms. With it, one may better grasp the complexity of the myriad treaties and agreements in, for instance, climate and energy governance and compare this with a governance architecture on oceans, biodiversity or chemicals. Such comparisons across institutional architectures and issue areas can reveal, especially, lower or higher degrees of governance fragmentation, which might influence performance of an architecture.We find governance fragmentation at all levels of political institutions, from local administrations up to national political systems and global governance. Architectures of global governance, however, fundamentally differ from national architectures. Within countries, the rights and responsibilities of political actors and institutions are defined in a written or unwritten constitution that lays down procedures in cases of institutional conflict and normative contestation. While this ideal-type description is rarely matched in realitywith political systems being often marked by constitutional ambiguity, conflict, overlap and crisisthe difference between national and global architectures is evident. Some observers see the Charter of the United Nations as a functional equivalent to national constitutions. But even then, global governance follows logics that differ from national political systems. At the global level, institutional fragmentation is much deeper, and it is ubiquitous.This fragmentation of global governance stands at the centre of this chapter. We start with a conceptualization of governance fragmentation and its relation to concepts such as polycentricity and institutional complexity. We then review the origins of governance fragmentation and its problematization; methodological approaches to studying fragmentation; and the impacts and consequences of fragmentation. We conclude by identifying future research directions in this domain.158