The common name blenny (deriving from the Greek  and , mucus, slime) is ambiguous at best, as it has been applied to several families of perciform marine, brackish, and some freshwater fishes all sharing similar morphology and behaviour. Six families are considered "true blennies", all grouped together under the suborder Blennioidei; its members are referred to as blennioids. About 833 species are found in 130 genera within the suborder.

The common name blenny (deriving from the Greek  and , mucus, slime) is ambiguous at best, as it has been applied to several families of perciform marine, brackish, and some freshwater fishes all sharing similar morphology and behaviour. Six families are considered "true blennies", all grouped together under the suborder Blennioidei; its members are referred to as blennioids. About 833 species are found in 130 genera within the suborder.