<p>The last few years have seen a multiplication of calls for placing the struggle against inequality and injustice at the heart of environmental activism and politics. Yet the articulation of environmental sustainability and social justice has been addressed in ways that sometimes reinforce the idea of necessary trade-offs between them. By contrast, the social sustainability perspective taken in this paper, and in this Special Issue, places social justice and equality at the heart of initiatives for ecological transformation. We apply this perspective to carry out a critical conceptual review of how different traditions of scholarship on agri-food systems transitions and transformations theorise, conceptualise, and research the relationship between inequality and unsustainability. We examine, successively, work on ‘sustainability transitions’, alternative food networks, food justice studies, critical agrarian studies, Global Value Chain perspectives, and, finally Black geographies, Plantationocene and Social Reproduction Theory approaches. Overall, our review shows that, while both inequality and unsustainability are discussed in the literature on agri-food systems transitions and&#xa0;transformations, the structural relationship between them, i.e. what we call the inequality/unsustainability nexus, is less fully theorised. We argue that a theorisation of the nexus, which draws on eco-Marxism and feminist critical theory as well as on insights from critical geographers, offers both a more structural approach, drawing attention to how social relations of inequality produced and reproduced by capitalism are central to the continued production of unsustainability—also in transition initiatives; and a more strategic approach, encouraging alliances starting from struggles for livelihoods and social equality to address environmental aims.</p>