Abstract Managing and modelling urban growth is a multi-faceted problem. Cities are now recognised as complex systems through which non-linear processes, emergence and self-organisation occur. The design of a system that can handle these complexities is a challenging prospect. This paper presents an urban planning application for the city of Riyadh, Saudi Arabia. At the core of the application is a Fuzzy Cellular Automata Urban Growth Model (FCAUGM) which is generally capable of simulating the complexities of urban growth. The chief components of the model are outlined and quantitative and qualitative methods of validation are described. The results of the validation show that the model is to a large extent successful at replicating the spatial patterns over time for Riyadh although closer examination reveals several minor anomalies which cannot readily be explained. The authors conclude that the model offers significant benefits for simulating urban growth and change, for urban planning and decision-support for policy makers and others, but further research will be necessary on methods of validating and interpreting the detailed results.