Rapid urbanisation and the exponential growth of consumption patterns have elevated solid waste management into one of the most pressing environmental governance challenges of the twenty-first century. Conventional waste management systems, characterised by fixed collection schedules, manual monitoring, and reactive logistics, are demonstrably incapable of addressing the scale, complexity, and real-time dynamics of waste generation in modern cities. This paper investigates Smart Waste Management Systems (SWMS) powered by the Internet of Things (IoT) as a transformative technological and governance response, and evaluates their alignment with and contribution to the United Nations Sustainable Development Goals (SDGs). Drawing on a systematic review of 54 peer-reviewed studies and technical reports (2016–2025), primary survey data from 140 urban waste management professionals and municipal officers across India, and three city-level case analyses (Pune, Singapore, and Amsterdam), the study examines the architectural components of IoT-enabled SWMS — including smart sensors, RFID tagging, GPS fleet management, cloud analytics, and AI-driven route optimisation — and evaluates their measurable environmental, economic, and social outcomes. Findings demonstrate that IoT-based SWMS deployments achieve a mean 38.4% reduction in collection vehicle fuel consumption, a 44.7% reduction in illegal dumping incidents, a 61.3% improvement in recycling diversion rates, and an average cost saving of 27.8% in municipal waste management budgets, while directly advancing SDGs 3, 6, 11, 12, 13, and 17. The paper concludes with the Smart Waste IoT Governance Framework (SWIGF), a policy roadmap for municipalities, technology providers, and national governments to accelerate responsible and equitable IoT-SWMS deployment at scale.