Atriotaenia sanmarci n. sp. (Cestoda: Anoplocephalidae) is described as a parasite of the Andean hog-nosed skunk, Conepatus chinga (Carnivora: Mephitidae), from Cusco, Perú. The new species is primarily distinguished from related species by the distribution, and greater number, of testes, i.e., 194–223 versus 40–60 in Atriotaenia sandgroundi (Sandground, 1926) Baer, 1935, 47–73 in Atriotaenia procyonis (Chandler, 1942) Spasskii, 1951, and 21–84 in Atriotaenia incisa Railliet, 1899. Also, there are differences with respect to the larger dimensions of suckers (300–371 µm vs. 140 in A. sandgroundi, 83–134 in A. procyonis, 70–140 in A. incisa, and 155–192 in Atriotaenia hastati Vaucher, 1982) and in the cirrus pouch length (204–732 µm vs. 90 in A. sandgroundi, 200–220 in A. procyonis, 100–180 in A. incisa, and 150–205 in A. hastati). The new species differs from A. sandgroundi and A. hastati in having a larger body size (122–133 mm vs. 10.6 and 10, respectively). This cestode is the fifth species of Atriotaenia Sandground, 1926.