||This dissertation aims to define the field of ecological planning. It uses interdisciplinary, mixed methods research to advance the understanding of theory, practice, and process at the intersection of science and the built environment. In theory, this dissertation defines ecological planning in terms of the "ecological paradigm": a concept elaborated by scholars of environmental history. This concept ties together the implicit theory of ecological planning, as described by experts within the field, and makes that theory explicit in one rigorous, coherent, interwoven analysis. As we will see, ecological planning is at the leading edge of a temporal, accretive, and aspirational shift to this paradigm, as both science and urbanism move towards one another into a new inter- or transdisciplinary space. In practice, this dissertation identifies the points of consensus that characterize research and application at the intersection of biophysical science and the built environment. It draws on the insights of expert scientists and urbanists, from both academia and professional practice, whose work focuses on that intersection. Their key points of agreement include principles for ecological planning practice, policies and governance structures, direct applications, the elements of successful projects, and the intricacies of interdisciplinary and collaborative work. In process, this dissertation creates a new conceptual framework for ecological planning which is holistic, nonlinear, dynamic, and collaborative. That framework synthesizes the workflow of diverse ecological planning experts, to show how processes of science and urbanism may become further integrated. It weaves the preceding theoretical and practical perspectives together, defining ecological planning as a form of transdisciplinary praxis. Using this new definition, the dissertation then assess the current state of ecological planning and makes recommendations for the field to realize its full potential, as the social-ecological future of planning in a social-ecological world.