This chapter focuses on sub-national challenges to the territorial sovereignty of the post-colonial state in Melanesia and their intersections with ethnic identity and violent conflict. It discusses work in human geography and political ecology on the social production of space, ‘governable spaces’, and the ‘politics of scale’. The chapter argues that islands have provided especially potent arenas, at particular moments and conjunctures, for the contentious political economic struggles that have attended colonialism and globalisation. The concept of ethnicity is much debated by social scientists, having been characterised as ‘elusive’ and ‘notoriously slippery’. At one end of the conceptual continuum, ethnicity is regarded as primordial or essential: ‘It exists in nature, outside time’. Ethnicity is seen as situational or constructed, with its boundaries and cultural contents regarded as mutable and fluid: ‘varying with the particular situation of the subject’. An important development in human geography over the past two decades or so has been the reconceptualisation of geographical scale.