This brief examines the evolution of the ‘Indo-Pacific’ concept in the context of the dynamic role of “regions” in international relations. It argues that the conception of these theatres is a consequence of power relations; that as power dynamics change, so does the conceptualisation of regions. This would also explain why the boundaries of regions can be arbitrary—why, for instance, the Asia-Pacific stops at Myanmar and does not include India; or why given Myanmar’s historic location within British India, it is excluded from South Asia. The brief says this seeming lack of rationality indicates that the boundaries of international regions are contingent on political interests.