The status of mammals in Europe was assessed according to IUCN Red List Criteria and regional Red Listing guidelines. We found that nearly one in six (15%) of Europe’s 231 mammal species were threatened (IUCN categories CR, EN, VU), with a further 9% considered Near Threatened. Marine mammals faced particularly high levels of threat, with 22% of marine species (n=27) versus 14% of terrestrial species (n=204) assessed as threatened. More than a quarter (27%) of mammals had declining populations. A further 32% were stable and 8% increasing; 33% were of unknown population trend. Terrestrial mammal biodiversity was greatest in south-eastern Europe (the Balkan Peninsula, Hungary, and Romania) and in the mountainous regions of Mediterranean and temperate Europe. Habitat loss and degradation was the greatest threat to terrestrial mammals in Europe, although human disturbance, pollution, accidental mortality (e.g., secondary poisoning, vehicle collisions), overexploitation and invasive species were also important. The main threats to marine mammals were accidental mortality (e.g., fisheries bycatch), pollution and overexploitation. EU Member States have committed to halt biodiversity loss by 2010, but the evidence from this study suggests that this target is unlikely to be met and significant actions must take place to halt the decline of mammal biodiversity in Europe. The results presented here provide a baseline against which future progress can be measured