The pupfishes are a group of small killifish belonging to ten genera of the family Cyprinodontidae of ray-finned fish. All pupfishes are especially noted for being found in extreme and isolated situations, in various parts of North America, South America, and the Caribbean region.
The common name is said to derive from the mating habits of the males, whose activities vaguely resemble puppies at play. Most pupfishes are inhabitants of the fresh and brackish waters of the Americas; a few species are known from the Old World. Many species are ovoviviparous, and from their small size and lively behaviour they are much appreciated as aquarium fishes.