This report provides the supporting science for the UNEP Science-to-Policy brief (2017). It synthesizes the current science on wastewater pollution and coral reefs to inform decision-making and policy globally. This synthesis will support decision-making and capacity building efforts at a regional level under the Global Wastewater Initiative, initially in the Caribbean and Red Sea region, and later in the Pacific region; to strengthen monitoring of wastewater loading and impacts among key stakeholder groups; and to raise awareness through Regional Seas and other relevant mechanisms. The report also provides the foundation and key recommendations for linking wastewater monitoring explicitly to coral reef status and resilience assessments. A wide range of wastewater compounds, including nutrients, pesticides, trace metals and petroleum hydrocarbons enter reef ecosystems through various pathways and affect reef species and/or life history stages. Many wastewater pollutants, including agricultural fertilizers, pesticides and organochlorine compounds, domestic and municipal wastes, trace metals and petroleum products are now recognized to have adverse effects on coral reefs, even when released at low levels. Understanding their impacts and the species that are sensitive to these pollutants is important for informing management and monitoring. The following topics are treated: Wastewater pollution and coral reefs: Primary sources; Wastewater pollution impacts on coral reef ecosystems; Wastewater pollution on reefs in the context of climate change; Managing wastewater pollution to minimize impacts on coral reefs; and Summary of pollutant-reduction management and effectiveness.