It is widely perceived that city-wide sanitation planning can enable coordinated improvements in efforts to achieve universal access to sustainable sanitation services in urban contexts in developing countries. However, it has been observed that city sanitation planning is not always effective and does not always lead to (in part or in full) sustainable and equitable outcomes. Indeed the planning process may or may not result in, or inform, implementation. This observation resonates with existing reviews and critiques of sanitation planning over the past decades (Kennedy-Walker et al. 2014; Luthi et al. 2011). A key factor to recognise is that in the majority of developing countries, demand for sanitation services by both citizens and politicians is low, and this strongly affects the potential for plans to be turned into reality. It is therefore important to reflect on and critically question sanitation planning in order to get the most value out of city sanitation planning processes and to approach such planning processes with realistic expectations. The aim of this Learning Paper by SNV and the Institute of Sustainable Futures (Sydney) is to provoke practitioners, policy makers and development agencies to reflect on their approaches to city sanitation planning and the assumptions that underlie them.