Historical GIS is an emerging field that uses Geographical Information Systems (GIS) to research the geographies of the past. The authors present the first study to define this emerging field comprehensively, exploring all aspects of using GIS in historical research. A GIS is a form of database in which every item of data is linked to a spatial location. This technology offers unparalleled opportunities to add insight to and rejuvenate historical research thought the ability to identify and use the geographical characteristics of data. Historical GIS introduces the basic concepts and tools underpinning GIS technology, describing and critically assessing the visualisation, analytical and e-Science methodologies that it enables, and examining key scholarship in which GIS has been used to enhance research debates. The result is a clear agenda charting how GIS will develop as one the most important approaches to scholarship in historical geography.