Prodistomum lichtenfelsi n. sp. (Digenea: Lepocreadiidae) is described; it was obtained from the intestine of the longtail bass, Hemanthias leptus (Ginsburg), collected from the Bay of Campeche in the Gulf of Mexico. This is the first record of a parasite from this host. Prodistomum lichtenfelsi n. sp. is similar to P. hynnodi, P. menidiae, and P. waltairensis in that it possesses a prepharynx that is distinctly shorter (153 μm [110–210] long) than the combined length of the esophagus (163 μm [110–220] long) and the pseudoesophagus (137 μm [120–170] long), but it differs from them in having an excretory vesicle that extends into the forebody, a smooth ovary and testes, and vitellaria that extend to the posterior level of the esophagus. An updated key to the 12 nominal species within Prodistomum is given, and the diagnosis of the genus is emended to include species possessing a sinuous external seminal vesicle.