Whipworms collected from llamas (Lama glama) in Oregon were identified as Trichuris tenuis Chandler, 1930. A redescription, based on the specimens collected from llamas and examination of the paratypes, is presented. The unique form of the cloaca in T. tenuis separates males of this species from all other species of Trichuris known to occur in ruminants. Among species of Trichuris for which adequate descriptions of the female exist, T. tenuis can be distinguished using an array of characters including an uneverted, aspinous vulva and a highly convoluted vagina with papillalike spines in the proximal one-fourth and a small egg chamber located approximately midway along its length. This constitutes only the second report of T. tenuis in North America and brings to 7 the number of species of Trichuris known to occur in sylvatic and domestic ruminants in North America.