Despite being identified by The Forum of Federations as one of the key trends in contemporary federations, the concept of ‘hourglass’ federalism remains somewhat nebulous. By analysing examples where the label has been applied, this paper begins to fill this conceptual lacuna. As a strategy, we argue that hourglass federalism is pursued for two primary purposes: improving local services and autonomy, while also consolidating national unity and political stability. As an institutional manifestation, we identify five features that define hourglass federal systems: 1) the constitutional allocation of powers to local government; 2) a direct financial relationship between local government and the centre; 3) local government accountability to its constituents; 4) local government representation in intergovernmental institutions; 5) dedicated local government bureaucracies. In concluding, we highlight future research directions to guide further analysis and evaluation of hourglass federalism.