The UK Checklist of Freshwater Species is a collation of all the species (apart from algae) known to be found in association with fresh waters in the United Kingdom. The following eight major groups were identified as being associated with fresh waters in the UK: algae, amphibians, birds, fish, invertebrates, macrophytes, mammals and reptiles. Algae (except stoneworts) were not included in the UK Checklist of Freshwater Species as they are currently undergoing a major revision. Other microorganisms (bacteria, fungi and viruses) are also not included in this species list. The checklist was compiled to allow querying of freshwater species data in the Biological Records Centre (BRC) but to also to query freshwater species data from the BRC via the UK Lakes Portal (https://eip.ceh.ac.uk/apps/lakes/), as well as to update the freshwater species list supplied to the UK Species Inventory (UKSI) partners, such as Recorder 6, National Biodiversity Network (NBN) Atlas and iRecord. Full details about this nonGeographicDataset can be found at https://doi.org/10.5285/57653719-434b-4b11-9f0d-3bd76054d8bd