Nature-Based Urbanism is the second volume of the Nature and Cities trilogy, advancing the case for embedding ecology into the core of urban planning, design, and governance. Building on the foundation established in Nature in Cities, Nurturing Cities, this book shifts from theory to practice, exploring how cities worldwide are integrating ecological systems as infrastructure for resilience, equity, and liveability. The volume brings together a wide spectrum of cases, from Southeast Asian green-space transitions and vernacular riverine landscapes to multispecies planning, nature-driven placemaking, and regenerative urban governance across India and Europe, to show how cities are re-imagining their relationship with nature. Throughout the case study chapters, ecological thinking transforms planning, design, and daily urban living as a theoretical lens and useful toolset. In addition to providing new avenues for participation, governance, and community agency, the contributions show how nature-based initiatives can address climatic volatility, biodiversity loss, social disintegration, and the deterioration of human-nature relationship. When taken as a whole, they show that incorporating nature into urban design is not just an environmental need but also a cultural and civic revolution that is now occurring in places all over the world. By uniting ecological restoration, biophilic design, and nature-based solutions under the framework of urbanism, this book positions cities as living ecologies rather than static built environments. Its intellectual ambition is to redefine urbanism as regenerative practice; its practical aim is to provide scalable models for professionals, policymakers, and communities. More importantly, Nature-Based Urbanism contributes to global debates on sustainability by making a bold claim: the future of urban life depends on building cities with nature, not against it.