Greenways is a landscape planning strategy of international interest. This paper includes a discussion of greenway definitions with an emphasis on their spatialplanning components. Three principle hypotheses that support greenways are discussed: 1) co-occurrence of greenway resources, 2) the inherent benefits of connectivity in greenway corridors, 3) the complementarity of multiple uses in greenways. Theory from landscape ecology provides a foundation for greenways regarding spatial configuration in general, and for connectivity in particular. The implementation of greenways provides both challenges and opportunities to address the integration of nature and culture in urban, metropolitan and rural landscapes around the world. Three brief case studies are presented to illustrate how greenways have been applied and developed in Western Europe and in the United States.