Bass /ˈbæs/ is a name shared by many different species of fish. The term both encompasses freshwater and marine species. All belong to the large order Perciformes, or perch-like fishes, and in fact the word bass comes from Middle English bars, meaning "perch."

The temperate basses, such as the striped bass (Morone saxatilis) and white bass (M. chrysops), belong to the family Moronidae. The black basses, such as the largemouth bass (Micropterus salmoides), smallmouth bass (M. dolomieu), spotted bass (M. punctulatus), Choctaw bass (M. haiaka), and Guadalupe bass (M. treculii), belong to the sunfish family, Centrarchidae.