This chapter makes the central argument that by drawing on alternative understandings of materiality and recognising the agency of nonhumans, the normative foundations and conceptual tools of global sustainability governance can be critically examined. Against such firmly held beliefs as the dualism of human and nonhuman worlds, a nonhuman agency perspective argues for their ontological interdependence and suggests research frameworks that make these entangled relationships and their implications for processes of sustainability governance visible. The chapter starts out by giving an account of how nonhuman agency can be understood and conceptualised, and how materiality can be thought of differently vis-à-vis its traditional uses. The concepts of hybrids and assemblages are introduced as two distinct approaches of how scholars have made sense of and analysed a world of interconnected and swapping agencies, before these discussions are illustrated by research conducted in the field of waste governance. The conclusion argues for broadening political recognition towards nonhumans as one way to organise political responsibility today and build strong institutions towards an ecologically safe and socially just future.