The issue of microplastics and nanoplastics within water bodies is alarming, owing to the ease with which microorganisms at different levels of the food chain ingest them. Microplastics are plastic particles whose diameters do not exceed 5 mm, and their presence in freshwater ecosystems poses serious environmental challenges. The aforementioned types of plastic waste originate from multiple sources, including but not limited to untreated domestic sewage waters, factory exhausts, storm waters, and agricultural runoffs resulting from urban land use activities. Rivers, lakes, and reservoirs are softer due to erosion over time and contain microplastics, which severely affect their ecosystems. Their flow velocity and turbulence in conjunction with seasonal rainfall determine their behaviour, while shape, size, colour, among other factors, provide information on where they originated. Environmentally persistent microplastics cause concern because these pollutants can lead to inflammation and reproductive distress, along with growth inhibition in aquatic organisms. Moreover, serving as transporters for parasites augments the threat that arises from toxins towards wildlife and the human population. This chapter outlines the issue of microplastic contamination within freshwater ecosystems, concentrating on its sources, spread, and environmental consequences. It focuses on the entry pathways of microplastics and their movement under different conditions, as well as the potential dangers to marine organisms. The chapter argues that integrated environmental science policy, engineering, alongside social behavioural frameworks, are needed in tackling microplastic pollution. Global action, collaboration across multiple disciplines, sustained research as well and advocacy are needed to mitigate the threat posed by microplastics. Research and policy initiatives designed to combat freshwater ecosystem pollution and strengthen their resilience will be underpinned by this chapter.