A new genus and species of captorhinid reptile from the Lower Permian Waggoner Ranch formation of north-central Texas, Reisz orhinus olsoni, is described on the basis of well-preserved cranial material. The holotypic specimen, consisting of a partial skull and mandible, was misidentifled by S. W. Williston in 1917 as Labidosaurus hamatus. Autapomorphies of the new taxon include recurved teeth and the possession of an extremely large Meckelian foramen on the medial surface of the lower jaw. The new taxon retains the primitive condition of a single row of dentary and maxillary marginal teeth. It is distinguished from other single-tooth-rowed captorhinids, with the exception of Labidosaurus hamatus, by its large size, and it lacks the marked cheek expansion found in other large captorhinids. PAUP and Bayesian analyses suggest the new genus is the most basal of described captorhinid genera with the exceptions of Romeria, Concordia, and Protocaptorhinus. The description of a new, large, single-tooth-rowed form suggests that, in addition to multiple tooth rows, relatively larger size evolved more than once in the basal reptilian family Captorhinidae.