The transition to a circular economy (CE) and green transition represents a pivotal shift in addressing global sustainability challenges. This introductory chapter delves into the fundamental principles of the circular economy and the green transition, elucidating their relevance to the Global South. The circular economy framework aims to redefine growth by decoupling economic activity from the consumption of finite resources, emphasizing restorative and regenerative approach. It contrasts sharply with the traditional linear economic model, which follows a ‘take-make-dispose’ pattern, leading to resource depletion and environmental degradation. Green transition encompasses a broader spectrum of environmental sustainability strategies, including renewable energy adoption, sustainable agriculture, waste management, and green industrial processes. It seeks to transform the socio-economic systems in a way that mitigates environmental impact, reduces carbon footprints, and fosters resilience against climate change. The chapter begins with a historical overview of the evolution of these concepts, tracing their roots from early environmental movements to contemporary policy frameworks. It then describes the fundamental principles underpinning the circular economy and explores how these principles can be operationalized in various sectors. Furthermore, the chapter discusses the relationship between green transition strategies and circular economy principles, highlighting synergies and potential conflicts. The chapter concludes with a discussion on policy implications, emphasizing the need for supportive regulatory frameworks, international cooperation and capacity building to foster a sustainable future. By presenting a holistic introduction to circular economy and green transition, this chapter sets the stage for deeper explorations in subsequent chapters, aiming to equip policymakers, researchers and practitioners with the knowledge and tools necessary to drive sustainable development in the Global South.