The central purpose of this chapter is to consider how complexity might usefully be applied to the study of regulation and regulatory systems. As with any field, one must be cautious when cross-applying a new and unfamiliar perspective and its associated methodologies to something like regulation. One of the central claims made here is that in order for this to be a meaningful exercise, complexity needs to piggyback onto existing concepts from regulation scholarship in order to distinguish and make sense of important patterns of relationships within a regulatory environment. It proposes that the concept of the ‘regulatory space’ can be a useful handmaiden for this purpose and offers a new conceptual framework of the ‘complex regulatory space’ as the outcome of their union. It explores what a complex regulatory space would look like and uses banking as an example to demonstrate how it can highlight the relationships, dynamics and tensions that give shape to patterns of banking actor behaviours and their relationship to systemic phenomena. It also locates the place of law in regulation, one that is necessarily ‘decentred’ as a contextual feature of actor behaviour rather than a core structural feature of regulation itself. Overall, the tone of this chapter is meant to be both exploratory and circumspect. Applying complexity to something like regulation is far from straightforward, but what it might sacrifice in simplicity it can exchange for greater nuance and new insights into regulation as a complex social phenomenon.