This study attempts to explore the effect of human territorial behaviour on shaping the Arab-Muslim built environment in the past, present and future. Also, the study establishes a continuity between the traditional and contemporary Arab-Muslim built environment, the case of Saudi Arabian neighbourhoods. To achieve these objectives the study starts by a critical review of the existing body of theoretical knowledge about human territorial behaviour phenomena in order to rationalise it and match it with the dynamic nature of the Arab-Muslim built environment. The thesis sees human territoriality as a spatial behaviour and traces it to its roots in the behavioural sciences, mainly Psychology and Sociology, and design as the art of space making. It proposes the human territorial behaviour phases (Allocation, Attainment, Maintenance, and Abandonment) in parallel to the built environment space design cases/stages (Nesting, Stringing, and Clustering).The study, then, reviews the historical knowledge about the traditional Arab-Muslim built environment, and investigates the origin and process of Arab-Muslim territoriality, and its effect on the built environment. This study looks at the Islamic law (Sharicah) ownership system and built environment easement rights as parameters for defining the Traditional Arab-Muslim built environment's various territorial types (Public and jurisdictional, semi public, semi private, and private and personal space). This distinction verified the common belief that the Arab-Muslim built environment is a result of its resident's continuous territorial encroachment on the available public spaces.The study not only depends on the theoretical and historical critique review, but also depends on analysing aerial photos of the Saudi built environment dated from 1935 until now. This analysis leaves little space for speculation about the process by which the Saudi built environment was formed and transformed. The study ends up with the possible notions which might be suggested by way of re-establishing a sense of continuity between the past, present, and future effect of human territorial behaviour upon the Arab-Muslim built environment in the case of Saudi Arabia towns. This is achieved through the re-introduction of the traditional Fina concept into the contemporary built environment as a means for realising its forgotten transformation characteristics at the street scale. This release is seen as a way of recycling the contemporary city spaces and governed by the designer, the neighbourhood local authority, and the city municipality.