Freshwater bivalves are a large, diverse and important group, since they can dominate the biomass of many ecosystems. Furthermore, they are among the world’s most imperiled taxonomic groups. Freshwater bivalves provide crucial ecosystem functions and services such as water purification and nutrient cycling, thus can be used as nature-based tools for improving ecosystem functions and services as well as representing important indicators of ecosystem health. Through the international cooperation of scientists from multiple disciplines, this Action will aim to fully understand the biodiversity crisis being faced by Europe’s freshwater mussels and develop evidence-based solutions to halt the loss of their biodiversity and ecosystem services.