The South Asian region faces pressing environmental concerns such as air pollution, biodiversity loss, and the degradation of land and water resources, compounded by the challenges of meeting the needs of growing populations. The region is interconnected by shared socioeconomic contexts and geographical features, including the Hindu Kush Himalaya mountain range, which influences climate patterns and serves as the source of transboundary rivers. Six of the eight South Asian countries share twenty major rivers, facilitating the transport of pollution across borders, including solid waste and microplastics. The study aims to shed light on the mounting concerns around inadequate waste management across urban and rural areas in the region, particularly the detrimental impact of plastic pollution, especially single-use plastics, on the environment and human health. The report seeks to establish a comprehensive baseline of plastic waste flow into water bodies in the region and support the formulation of evidence-based policies and strategies for plastic pollution reduction and a transition toward a regional circular economy framework for plastics. The study also highlights the need for interventions along the entire value chain, including reducing or substituting the use of plastics, introducing a reduce, reuse, and recycle (3R) hierarchy, implementing efficient collection and recycling systems, and enhancing waste management and treatment infrastructure. The report emphasizes the importance of coordinated efforts and improved policy implementation to effectively reduce plastic consumption, manage plastic waste, and mitigate marine pollution across South Asia.