“Novel entities” can broadly be defined as “things created and introduced into the environment by human beings that could have disruptive effects on the earth system.” These may include synthetic organic pollutants, radioactive materials, genetically modified organisms, nanomaterials, and/or micro-plastics. This report, a background paper prepared for the Global Environment Facility (GEF), presents the results of a process developed to systematically identify novel entities that are relevant to the GEF. It then advises the GEF on how it might respond to the challenges and opportunities that they present. The process involved the identification of a broad range of novel entities, which were then narrowed down to a group of those most pertinent to the work of the GEF.