Combtooth blennies are blenniiformids; percomorph marine fish of the family Blenniidae, part of the order Blenniiformes.

By far the largest species is the eel-like hairtail blenny at 53 cm in length; most other members of the family are much smaller.

Small benthic crustaceans, mollusks, and other sessile invertebrates are the primary food items for most species; others eat algae or plankton.

Species of the genera Aspidontus and Plagiotremus (such as the false cleanerfish) are noted for their cunning mimicry of cleaner wrasses: by imitating the latter's colour, form, and behaviour, the blennies are able to trick other fish (or even divers) into letting down their guard, long enough for the blennies to nip a quick mouthful of skin or scale.

The fry of some species undergo an 'ophioblennius' stage, wherein the fish are pelagic (i.e., inhabiting the midwater) and have greatly enlarged pectoral fins and hooked teeth.