This dataset comprises weekly water quality monitoring data of seven sites along the River Thames, UK, and sixteen of its major tributaries from Feburary 2009 to December 2023. Monitored determinands include major nutrient fractions, anions, cations, metals, pH, alkalinity, and chlorophyll. This catchment-wide biogeochemical monitoring platform captures changes in the water quality of the Thames basin during a period of rapid change, related to increasing pressures (due to a rapidly growing human population, increasing water demand and climate change) and improvements in sewage treatment processes and agricultural practices. The dataset provides the research community with a valuable data and modelling resource for furthering our understanding of pollution sources and dynamics, and vital underpinning environmental data required to best manage this vital drinking water resource, which is key for the sustainability of the city of London and the wider UK economy. Full details about this dataset can be found at https://doi.org/10.5285/703af27b-ce8c-44e0-ac20-b46e391a64ef
