This chapter introduces an important concept in architectural analysis, the isovist. Along with two associated concepts—the isovist field and the visibility graph—the isovist provides a mathematical basis for analyzing and shaping architectural space and form. Significantly, isovists can also be used to investigate and even predict human behavioral and cognitive responses to buildings. This chapter commences with an overview of both the isovist and isovist field, before describing their origins and applications. The chapter also presents a summary of past research that uses isovists to analyze architectural and urban space or seeks to correlate isovist measures with human perceptions. While the chapter does not provide detailed explanations of all the mathematical and computational processes involved, it does include a list of key isovist measures and their behavioral interpretations. The references cited in this chapter include detailed worked examples of isovist analysis along with discussion of limitations and recent developments.