This article offers an experiment in theorising within or across a ‘space’ of ontological disagreement – which, as numerous authors have contended, characterises much that is at stake in relations between states and Indigenous peoples in the Americas. Such ontological disagreements, I argue, contain radical potential for disrupting globally dominant and anthropocentric patterns of thinking and relating, and for generating alternatives. I substantiate this point with reference to the relational ontologies informing different Indigenous ways of analysing and practicing existence. Drawing on Amazonian Kichwa thinking and Anishinaabe accounts of treaties, I show how these relational ontologies recast the problem of how it is possible to relate with difference, in such a way as to fold an inter-human ‘international’ into a continuum of relations that include human-nonhuman ones. Distinct normative horizons emerge. I argue that non-Indigenous people can draw a range of provocations here concerning our constitution as selves and the political space in which we understand ourselves to possibly participate. I also claim, however, that this more transformative potential is predominantly squandered through processes of what I call ontological capture, which troublingly re-entrench dominant construals of reality and forestall a more radical questioning and re-patterning of accompanying lifeways.