Urban planning in many parts of the world reflects an increasing gap between current approaches and growing problems of poverty, inequality, informality, rapid urbanisation and spatial fragmentation, particularly (but not only) in cities of the global South. Given past dominance of the global North in shaping planning theory and practice, this article argues that a perspective from the global South can be useful in unsettling taken-for-granted assumptions about how planning addresses these issues. The article takes a first step in this direction by proposing a 'clash of rationalities', between techno-managerial and marketised systems of government administration, service provision and planning (in those parts of the world where these apply) and increasingly marginalised urban populations surviving largely under conditions of informality. It draws together theoretical resources beyond the boundaries of conventional planning theory to understand the nature of this conflict, and the nature of the 'interface' between those involved, where unpredictable encounter and contestation also open the possibility for exploring alternative approaches to planning.
