Freshwater mussels occurrences in Wallonia is a presence-only occurrence dataset dedicated to mussels observations (Unio crassus, U. pictorum, U. tumidus, Anadonta anatina, A. cygnea and Pseudanodonta complanata) made by the Département d'Etude du Milieu Naturel et Agricole (SPW-DEMNA) and partners, between 2002 and 2020. The data were collected within the framework of the department's missions, mostly related to the Natura 2000 monitoring and reporting and the LIFE Belgian Nature Integrated Project (BNIP). This dataset includes only verified presence records but some populations have disappeared during the period covered. It should be considered as an historical monitoring of the remaining populations and caution should be paid on the dates of the records. The absence of data does not always mean that the species is not present and absence data were not included in the dataset to avoid their misinterpretation but are available by request adressed to the Department. Please feel free to contact the department if you have remarks/questions regarding the dataset or about freshwater mussels monitoring.