Priapella is a small genus of livebearing fish in family Poeciliidae, the same family that gives the hobby its guppies, mollies, platies, and swordtails. It is endemic to Mexico, restricted in the atlas to Atlantic-slope drainages running toward the Gulf of Mexico. Atlas species measure 2–3 in and, like other poeciliids, the males carry a modified anal fin (a gonopodium) used to internally fertilize females, which then give birth to free-swimming young rather than laying eggs. The genus sits close to Xiphophorus and Poecilia in the livebearer family tree, and several of its species are narrow-range endemics found in only one or a few river systems.
Priapella is far less familiar to hobbyists than its guppy and swordtail relatives, though a handful of species have circulated among livebearer specialists - Priapella compressa, the Palenque priapella, and Priapella olmecae, the Olmec priapella, are among the names most likely to turn up. Their restricted Mexican ranges leave the genus more exposed to habitat loss than widespread livebearers, and the atlas reflects that: of the six species assessed, three are Data Deficient, one is Endangered, and only one is confirmed Least Concern. Two atlas species carry CARES Preservation Program status, marking them as priorities for hobbyist-maintained breeding populations as a hedge against disappearing in the wild.