Poecilia sphenops is a species of fish, of the genus Poecilia, known under the common name molly; to distinguish it from its congeners, it is sometimes called short-finned molly or common molly. 

They inhabit freshwater streams and coastal brackish and marine waters from Mexico to Colombia. The wild-type fishes are dull, and silvery in color. The molly can produce fertile hybrids with many Poecilia species, most notably the sailfin molly. The male mollies generally tend to be mildly aggressive.