This chapter explores the critical role of built environments in shaping physical activity behaviour among urban populations worldwide. As most of the world¿s population now resides in urban areas, the design of built environments¿encompassing buildings, transport systems, streets, and open spaces¿profoundly influences opportunities for active living. The chapter reviews evidence linking built environment features, such as walkable neighbourhood design, active transport infrastructure, and public open spaces, to physical activity for transport and recreation, which are two key domains for meeting physical activity targets and promoting population health. It underscores the importance of inclusive, age- and child-friendly urban design and transport planning for promoting physical activity across the life course. The chapter highlights inequities in access to activity-friendly environments within and between cities internationally, particularly in LMICs, and the need to address environmental hazards that are interconnected with physical activity, such as urban heat and air pollution. Finally, the chapter provides guidance for future research and for urban policymakers and practitioners, emphasising the need for evidence-based strategies to create equitable and sustainable cities that support physical activity and health for all.
