Aztec or Nahuatl writing is a pictographic and ideographic pre-Columbian writing system used in central Mexico by the Nahua peoples. The majority of the Aztec codices were burned either by Aztec tlatoani (emperors), or by Spanish clergy following the conquest of Mesoamerica. Remaining Aztec codices such as Codex Mendoza, Codex Borbonicus, and Codex Osuna were written on deer hide and plant fiber.

Aztec writing, however, is not considered to be a complete writing system that can communicate everything that can be expressed verbally and understood without a great deal of contextual information. This is because there is no complete set of characters that map to every verbal element in Nahuatl. The writing system is believed to be more of a mnemonic device to record tributary obligations, simple chronologies and the like. For this reason, Aztec writing is considered to be a proto-writing system.

The Aztec writing system is adopted from writing systems used in Central Mexico, such as Zapotec writing. Mixtec writing is also thought to descend from the Zapotec. The first Oaxacan inscriptions are thought to encode Zapotec, partially because of numerical suffixes characteristic of the Zapotec languages.