Xiphophorus is a genus of euryhaline and freshwater fishes in the family Poeciliidae of order Cyprinodontiformes, native to Mexico and northern Central America. 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. The name Xiphophorus derives from the Greek words ξίφος (dagger) and φόρος (bearer), referring to the gonopodium. All are small fishes, which reach maximum lengths of 3.5–16 cm (1.4–6.3 in) depending on the exact species.