The bullhead (Cottus gobio) is a freshwater fish that is widely distributed in Europe, mainly in rivers. It is a member of the Cottidae family, a type of sculpin. It is also known as the miller's thumb, freshwater sculpin, common bullhead or European bullhead.
The bullhead is a small demersal fish that lives both in cold, clear, fast-slowing small streams and in middle-sized rivers. It also occurs on gravelly shores of cold lakes. Further, it thrives in diluted brackish water of the Northern Baltic Sea. Its food items include benthic insects and crustaceans. On reproduction, it attaches its eggs in clumps on undersides of large stones.