A new Pliocene river otter is described from the Hagerman Fossil Beds (Hagerman Fossil Beds National Monument), Idaho. Lontra weiri, sp. nov., exhibits notable lutrine traits that closely align it to Old World Lutra and New World Lontra, which are morphologically similar but diphyletic. It is further assigned to Lontra based on known otter biogeography and molecular phylogenetic data. The Hagerman Fossil Beds are characterized by a Blancan North American Land Mammal Age fauna, and radiometric dates for the otter-bearing deposits are inferred as >3.79 Ma, making this the first pre-Pleistocene occurrence of Lontra. Hagerman has a rich and diverse carnivoran fauna with at least five families and 17 species represented, including a much larger otter, Satherium piscinarium. This new otter increases carnivoran richness at Hagerman and provides insight into the evolution of New World river otters.