Periurban areas are transition zones between rural and urban areas that are experiencing mixed land use, stress on natural resources, and social heterogeneity. Water security in periurban areas is shaped by the insecurity of land tenure as urban expansion claims more land and water sources. The most vulnerable residents are those who rely most on land near cities that is at risk of acquisition, have few alternative assets, and those whose social networks have been eroded. Addressing periurban water insecurity requires recognizing the interconnectedness of urban and rural water supply, supporting research on these areas, and basing urban planning on sustainable carrying capacities.