Dikerogammarus villosus, also known as the killer shrimp, is a species of amphipod crustacean native to the Ponto-Caspian region of eastern Europe, but which has become invasive across the western part of the continent. In the areas it has invaded, it lives in a wide range of habitats and will kill many other animals, often not eating them. It is fast-growing, reaching sexual maturity in 4–8 weeks. As it has moved through Europe it threatens other species and has already displaced native amphipods as well as other amphipods which had invaded areas previously.