Astacus is a genus of freshwater crayfish found primarily in Europe and parts of Asia. These crustaceans are known for their hard exoskeleton and pincers, which they use for defense and foraging. They typically inhabit rivers, lakes, and ponds, preferring clean, oxygen-rich waters. The most well-known species within this genus is the Astacus astacus, commonly referred to as the European crayfish. This species plays a vital role in its ecosystem, helping to maintain the balance of aquatic life by feeding on detritus and small organisms. However, it faces threats from habitat loss and invasive species.