The fourth edition of the Red List of Liverworts and Hornworts of Poland was prepared using the rules presented in the 2nd edition of the International Union for Conservation of Nature Red List Categories and Criteria (version 3.1). Altogether, 240 liverwort and four hornwort species that are currently found in Poland are included. Seventy-two species (71 liverworts and one hornwort) are classified as threatened, which comprises 30% and 25% of the liverwort and hornwort flora, respectively. The critically endangered (CR) category is assigned to 11 liverworts and one hornwort, the endangered (EN) category is assigned to 21 liverworts, and the vulnerable (VU) category is assigned to 39 liverworts. Two liverwort species, Anastrophyllum donnianum and Biantheridion undulifolium, are considered regionally extinct. Data concerning the distribution, abundance and population state of 21 species (20 liverworts and one hornwort) fall within the data deficient (DD) category; in this category, the data are insufficient for the established criteria to be used to determine the endangerment category. One liverwort is included in the not applicable (NA) category.