Nexus file of concatenated 18S, 28S, 16S and cox1 alignment with exclusion set indicated. This dataset was used to produce the main tree figure.A new species of proteocephalid cestodes, provisionally assigned to the non-monophyletic Ophiotaenia La Rue, 1911 (Cestoda: Proteocephalidae), is described from Compsophis infralineatus (Günther) (Serpentes: Pseudoxyrhophiidae) endemic to Madagascar. The new species, Ophiotaenia oreae n. sp. differs from all African and Asian species of Ophiotaenia from reptiles by possessing more uterine diverticula (68–82 on one side). It is also characterised by the absence of an apical organ, the relative sizes of the cirrus-sac and ovary, the almost equatorial position of the gonopore, the diameter of the embryophore, and other biometric characteristics. This is the fourth proteocephalid species described from Madagascan snakes. Phylogenetic relationships of the new species indicate its relatedness to Indomalayan and Australasian proteocephalids from reptiles. Ophiotaenia oreae formed a well-supported clade composed of species of the recently erected genus Australophiotaenia de Chambrier, Beveridge and Scholz, 2018 from Australian snakes, Macrobothriotaenia ficta (Meggitt, 1931) from the sunbeam snake Xenopeltis unicolor Reinwardt in Boie (Ophidia: Xenopeltidae) from Vietnam, Ophiotaenia sp. from Trimeresurus flavomaculatus (Gray 1842) from the Philippines, and Ophiotaenia bungari de Chambrier, Binh & Scholz, 2012 from Bungarus fasciatus (Schneider) (Ophidia: Elapidae) from Vietnam. The only proteocephalid from Madagascan snakes sequenced so far, Ophiotaenia lapata Rambeloson, Ranaivoson & de Chambrier, 2012 from Madagascarophis colubrinus (Schlegel), although closely related to the new species, they do not form a monophyletic group. The actual species diversity of reptilian cestodes in Madagascar is undoubtedly underestimated. Because of the assumed strict (oioxenous) host specificity of reptilian proteocephalids and rich fauna of snakes occurring in Madagascar, it is plausible to expect the existence of dozens new species of proteocephalids on this island.