Heterandria is a genus of livebearing fishes within the family Poeciliidae.

Most species occur in Guatemala and its surroundings, particularly Mexico, but the midget livebearer (H. formosa) comes from the southeastern United States.

Though many Poecilidae are familiar aquarium fishes, e.g. guppies, mollies, platys and swordtails, species within Heterandria are not commonly kept as pets.

Species in this genus resemble egg-laying Cyprinodontoidei such as Fundulidae (topminnows) at first glance, and are thus sometimes called "killifish" though this is technically erroneous.

[5][6][7] There are probably more remaining undiscovered[citation needed] as these fishes are rather inconspicuous.