Sierra Popoluca, also sometimes referred to as Soteapanec, Soteapan Zoque, or Highland Popoluca, is a Mixe–Zoquean language of the Zoquean branch. It is spoken by 28,000 (INALI 2008, based on INEGI 2000, 2005) indigenous Popoluca people in and around the town of Soteapan in the Sierra de Los Tuxtlas in southern Veracruz, Mexico. The speakers themselves call their language Nundajɨɨyi which means "true speech", and themselves Nundajɨypappɨc.
Towns where the language is spoken include San Pedro Soteapan, La Piedra Labrada, and Santa Rosa Cintepec. The Nahuatl language is also spoken in nearby Mecayapan, Tatahuicapan de Juárez, and Pajapan, and has influenced Sierra Popoluca as well.