Sovereignty is mostly articulated through a paradigm of inter-state compestition over resources and borders, in order to facilitate accumulation and control. Although its current appeal dates back to the seventeenth century and the Westphalian system, the definitions thus far privileged by the so-called international order have mostly worked against the interests of peoples and territories subject to (neo)colonial power, imperialism, and resource grabs. This paper interrogates how the ideology of ‘national interest’ is mobilised by states to advance expansionist interests in ways that disregard planetary boundaries and solidaristic cooperation among peoples, ultimately to the detriment of demands for self-determination, and to the possibility of building the ecosocial just transitions necessary for overcoming the polycrisis. In counterpoint, it suggests the need for a framework of popular and ecological sovereignty aimed at securing mutual survival and longevity, which will mean learning from movements and political organisations that challenge the capital-nation-state fantasy of limitless growth, in order to reformulate the basis for production and consumption in accordance with radical sustainability and a good life for the world’s majority.