Despite a greater acknowledgement of the role that urbanisation plays in sustainable development, there are, however, persistent blind spots in the understanding of how urbanisation operates as a particular socio-spatial process of metabolising nature and social relations. This chapter examines the so-called ‘urban transitions’ faced by the global south today, by zooming into the processes of unequal peri-urbanisation that characterise many urban regions of the global south today. The central argument is that the emerging peri-urban geographies are increasingly being shaped under conditions of ‘differential sustainability’, that is by adjusting thresholds to meet the needs and wants of certain privileged social groups and territories at the expense of others. In this context, the alleged ‘fuzzy regulation’ of land and ecosystem services that often characterises peri-urbanisation processes can also be interpreted as a deliberate strategy that assists the economic liberalisation of urban expansion, pawning the sustainability of vital ecosystem services and reinforcing the invisibility of the peri-urban poor both as producers and rightful citizens. Drawing from a wide-range of contexts across the global south, the chapter adopts a political ecology perspective to explore how differential sustainability is being produced, reproduced and challenged, with what consequences and for whom.