This book constitutes the proceedings of the 11th International Conference on Spatial Information Theory, COSIT 2013, held in Scarborough, UK, in September 2013. The 28 papers presented in this book were carefully reviewed and selected from 62 full paper submissions. The following topics are addressed: spatial change, wayfinding and assistance, representing spatial data, handling language data, spatial language and computation, spatial ontology, spatial reasoning and representation.