This chapter provides the framework and rationale for Greening the Greyfields and its two new models for greyfield precinct regeneration (GPR): place-activated and transit-activated GPR. They provide a basis for regenerative urban redevelopment in the middle-ring greyfield suburbs of fast-growing, low-density cities. Place-activated GPR advances a new development model for the ‘missing middle’ in cities: new medium-density housing at precinct scale. Transit-activated GPR extends new sustainable modes of mobility into car-dependent suburbs. Both processes are required for retrofitting suburbia to fix the shortcomings of mid- to late-twentieth-century urban planning and development.