Tehuantepec (tāwäntāpĕk´), officially Santo Domingo Tehuantepec (sän´tō dōmĬng´gō), town (1990 pop. 33,445), Oaxaca state, S Mexico, on a wide bend of the Tehuantepec River not far from the Gulf of Tehuantepec, an arm of the Pacific. The town is on the Isthmus of Tehuantepec. The climate is hot and humid. The population is largely Zapotec. Tehuantepec is the commercial and social rival of Juchitán.