Two new species of freshwater crabs of the genus Tehuana from the states of Tabasco and Oaxaca, Mexico, are described, and a new diagnosis for the genus is presented. Tehuana chontalpaensis, new species, was collected in a mountain river in southwest Tabasco at 900 m above sea level; it is distinguished by a first gonopod with an elongated mesial process and a large laminar lateral process with a strong lateral spine. Tehuana jacatepecensis, new species, was collected in the Jacatepec river, in central Oaxaca; it differs from other species in the genus by the first gonopod, which has a reduced, spoon-like lateral process and an ax–shaped mesial process that projects beyond the marginal process.