The taxonomic status of the genus Oxymycterus in Uruguay is assessed through morphologic, morphometric, and molecular comparisons with other species in the genus. Our analyses uncover the existence of a previously undescribed species, described herein, and restrict O. nasutus to SE Uruguay and SE Brazil. Uruguayan species are morphologically similar but differ substantially in sequences of the mitochondrial cytochrome-b gene. In contrast, O. rufus was found to be morphologically distinct from O. nasutus and the new species but genetically similar to the new species. Phylogenetic analyses lack resolution at the base of the genus but suggest well-supported relationships between O. amazonicus and O. delator, O. quaestor and O. judex, and O. rufus and the new species.