San Jeronimo Acazulco Otomi, or Ocoyoacac Otomí, is a moribund and seriously endangered native American language spoken by a hundred or so people in the town of San Jerónimo Acazulco in Ocoyoacac, Mexico State. Only people born before c. 1950 are fluent, and all of them speak Spanish on a daily basis. Acazulco Otomi has been classified as Eastern Otomi by Lastra (2006). It is more conservative, and closer to Eastern Highland Otomi, than is neighboring Tilapa Otomi. There are revitalization efforts underway.
Acazulco Otomi has ejective consonants as well as aspirated stops which correspond to fricatives in other varieties of Otomi, and is similar to reconstructions of the Proto-Otomi language.