The swordtail platyfish (Xiphophorus xiphidium) is a species of ray-finned fish within the family Poeciliidae.

[2] The species is endemic to the Soto la Marina River basin in Tamaulipas and Nuevo Leon.

It lives in springs, streams, arroyos, ditches, marshes, and ponds in slow-flowing clear to muddy waters, often over mud, clay, gravel, and rock where vegetation is typically abundant.

[3] There are currently no conservation efforts towards the swordtail platyfish, however its range does overlap in the Altas Cumbres Protected Area outside of Ciudad Victoria.

Threats such as cattle ranching degrading coastal streams and rivers due to runoff and water management in the Soto la Marina River are potential threats to the species, however the exact impact isn't known.