Xiphophorus is a genus of euryhaline and freshwater fishes in the family Poeciliidae of order Cyprinodontiformes. The many Xiphophorus species are all called either platyfish (or platies) or swordtails. The type species is X. hellerii, the green swordtail. Platyfish and swordtails are live-bearers, meaning that they reproduce via internal fertilization. Three species and their hybrids are common in the aquarium trade: the green swordtail (X. hellerii), the southern platyfish (X. maculatus) and the variable platyfish (X. variatus).
The various Xiphophorus species are native to areas of Belize, Guatemala, Honduras, and especially Mexico. All small fishes, which reach maximum lengths of 3.5–16 cm (1.4–6.3 in) depending on the exact species.