Rapid urbanization is straining material, water, and energy systems; this chapter positions circular supply chains as the mechanism to reclaim these flows and build regenerative, climate-resilient cities. We synthesize principles—closing loops, cascading use, regenerative design, design for disassembly, and urban mining—into a scheme that links four recovery streams (organics, water, energy, materials/products) with enabling capacities: reverse logistics, digital traceability (IoT, AI, blockchain), distributed recovery hubs, and inclusive networks spanning municipalities, businesses, informal workers, and citizens. Governance levers (policy coherence, urban planning tools, PPPs, and blended/green finance) and performance dashboards (MFA, urban metabolism indicators) operationalize and scale interventions. Anticipated outcomes include reduced landfill dependence, lower emissions, and decreased virgin extraction, alongside the creation of green jobs and benefits to resilience. We also map persistent barriers—institutional gaps, technical and infrastructure limitations, cultural resistance, and market immaturity—and propose pathways using modular design, product passports, and data-driven decision-making to mainstream circularity across urban systems through adaptive governance and cross-sector partnerships worldwide.