Poecilia petenensis, the Petén molly, is a poeciliid fish species endemic to Guatemala.

[2] When Rosen and Bailey (1963) revised the poeciliids, they placed both the swordtail and the short-finned molly in the genus Poecilia and made the short-finned species a synonym for Poecilia sphenops.

[2] Meyer et al. hold that Poeser (2002) broke nomenclature codes.

The body is relatively slender, more so than in the otherwise similar species P. teresae, and somewhat higher in the males than in the females.

[2] Poecilia petenensis is endemic to the freshwater Lake Petén Itzá in Guatemala.