Hñähñu, known in Spanish as Otomí, belongs to the Otomanguean family, one of the oldest and most diverse in Mesoamerica, within the Oto-Pamean branch. The Otomí are among the most ancient Indigenous peoples of central Mexico, predating the arrival of the Nahuas in the highlands.

About 300,000 people speak Hñähñu, mainly in Hidalgo, Querétaro, the State of Mexico, Veracruz, Puebla, and Guanajuato. The ñäñho/ñähñu people are known for their work with the maguey—from which they obtain pulque, ixtle fiber, and amate paper—and for a deep relationship with the Mezquital Valley.

Many Otomí were key allies during the conquest and colonization of northern Mesoamerica, founding or repopulating towns on the Chichimec frontier. Missionaries wrote grammars and catechisms in Otomí, though its tonal and nasal system made it hard to represent with the Spanish alphabet, producing several competing orthographies.

Hñähñu is classified as definitely endangered: transmission to children has declined in many communities. INALI writing standards, Indigenous radio, school materials, and community projects seek to revitalize the language and strengthen linguistic pride.