Onchocerca gutturosa and O. lienalis are redescribed and comparative morphological descriptions provided. In addition, a third species of Onchocerca is described from cattle in the United States. This third species, Onchocerca stilesi sp. n., localizes in the connective tissues around the stifle joint, and can be distinguished morphologically from O. gutterosa and O. lienalis. Onchocerca gutturosa and O. lienalis apparently have widespread distribution in the eastern United States; however O. stilesi has been reported only from Minnesota.