Serpentirhabdias dubielzigi n. sp. is described from Python regius from 2 separate locales in the United States. Many nematodes were observed in the eye, mouth, and subcutaneous tissues of 3 clinically affected, captive-bred, and captive-reared ball pythons. Although intact adult nematodes were not available for examination from the 2 Wisconsin, U.S.A., snakes, nematodes seen in histological sections from these cases and from the single Virginia, U.S.A., case were identical. The new species is described based on morphological characters of adult specimens obtained from formalin-fixed material from the Virginia case, and nematodes in histological sections from all cases. The designation is further supported by phylogenetic analysis of the nematodal internal transcribed spacer (ITS) 1 region of ribosomal DNA (rDNA) obtained from an affected Wisconsin snake. The nematodes involved in these infections are distinct from currently described species of Serpentirhabdias in the family of the host parasitized, the sites of infection, the possession of double lateral alae and very long excretory glands on adult nematodes, the possession of single lateral alae on larvae in eggs, and a unique genetic sequence of the ITS1 region of rDNA as compared with currently reported sequences in GenBank.