The use of floating photovoltaic systems in freshwater and marine environments is forecast to increase dramatically worldwide within the next decade in response to demands for accelerated decarbonisation of the global economy whilst avoiding competition for land, particularly near population centres. The potential environmental impacts of this expanding, novel technology are gradually becoming apparent and warrant consideration. This study reviews and evaluates the various potential environmental impacts of introducing floating photovoltaic arrays into aquatic (freshwater and marine) ecosystems based on the current state of floating photovoltaic technology and known impacts of similar industries. Environmental impacts of floating photovoltaic systems fall into several categories including shading, impacts on hydrodynamics and water-atmosphere exchange, energy emissions, impacts on benthic communities, and impacts on mobile species. The social acceptability of floating photovoltaic systems and the ability for long-term coexistence with other activities and interests are also discussed. Floating photovoltaic systems have an important role to play in global decarbonisation, but close collaboration between stakeholders will be required to better understand potential environmental and social impacts of this new technology. Development and validation of appropriate monitoring methods at scale, and consideration of long-term, equitable solutions to identified impacts, is important to enable sustainable expansion of this industry.