This dataset provides details of the first records of the bryophytes listed from Britain and Ireland by Blockeel et al. (2021) in A census catalogue of British and Irish bryophytes 2021 (published by British Bryological Society). For further details, and an analysis of the dataset, see the two papers by M.O. Hill and C.D. Preston (2024) ‘Discovery of British and Irish bryophytes 1. Trends in the detection and reporting of new species, 1538–2021’ and ‘Discovery of British and Irish bryophytes 2. Publication of finds in floras, checklists and papers, 1690–2021’ in Journal of Bryology 46(2).