This chapter explores the challenge of PPB in an urban world. Liveable cities and regions will depend on vital elements for human health including fresh water, air quality, biodiversity, landscape, and ocean conservation. The planetary boundaries framework is constructed around nine critical processes, including climate change, change in biosphere integrity, stratospheric ozone loss, land-system change, and others, that together define a state of the ES, with control variables identified for each process. The planetary boundaries framework, in addition to defining the safe operating zone (SOS), identifies a zone of increasing risk and a region of high risk through which the ES as whole could be tipped into a new state. A green-yellow-red ‘traffic lights’ approach is used to define the regions within the planetary boundaries framework. The development of planetary boundaries and the definition of an SOS are based on the state of the physical ES that is vital for planetary health, that is, for all living things (air, water and ecosystems). The SOS provides the foundation for a healthy and sustainable urban future. PPB contributes to an SOS to implement the United Nations SDGs and develop more sustainable pathways for cities and regions. By encouraging consideration of the key planetary boundaries in day-to-day urban decision-making (e.g., carbon, water, air pollution, biodiversity, land-system change and oceans), PPB provides an essential health check for urban environments. This chapter concludes that the cumulative impact of every city or town considering these essential planetary processes in planning decisions provides a strong basis for a more environmentally sustainable future.