any of numerous species of fishes of the family Serranidae (order Perciformes), many belonging to the genera Epinephelus and Mycteroperca. Groupers, widely distributed in warm seas, are characteristically large-mouthed, rather heavy-bodied fishes that tend to remain in discrete areas. Some are very large fishes, attaining a length and weight of about 2 metres (6 feet) and 225 kilograms (500 pounds)—in some instances reportedly much more. Groupers are often dully coloured in greens or browns, but a number are brighter, more boldly patterned fishes. Some, such as the Nassau grouper (Epinephelus striatus), are noted for their ability to change from one to any of a number of other colour patterns. Also, in many species, such as the blackfin and yellowfin groupers (Mycteroperca bonaci and M. venenosa), individuals inhabiting deeper waters are much redder than those living near shore. Groupers are protogynous hermaphrodites; that is, they first function as females and later transform into males. Groupers are prime food fishes and may also provide sport for anglers and spearfishermen. A few, however, may carry a toxic substance in their flesh and can cause ciguatera, a form of poisoning, when consumed.

One of the largest and best known of the groupers is the jewfish (q.v.). Other well-known species include the golden-striped grouper (Grammistes sexlineatus), an Indo-Pacific fish about 25 centimetres (10 inches) long, marked with rows of dashes when young but black or brown with lengthwise, yellow stripes as an adult; the Nassau grouper, an abundant Caribbean food fish about 90 centimetres long, varies in colour from white, with or without darker markings, to dark brown or gray brown; the red grouper (Epinephelus morio), another variable Caribbean food fish, usually reddish with pale blotches and about 90 centimetres long; and the rock hind (E. adscensionis), an Atlantic food species spotted with orange or red and about 60 centimetres long.