What was the Aztec hereditary noble class called?

The Aztec hereditary noble class was called the pipiltin. Pipiltin is the plural form; an individual noble was a pilli. The class formed the hereditary elite of Mexica society and supplied many of the empire’s rulers, senior officials, military commanders, ambassadors, and priests.

Noble status was associated with descent from established ruling families and with control of land, labor, education, and political offices. Members of the pipiltin could head noble houses known as tecalli and enjoyed privileges in clothing, housing, education, and access to government positions. Their children were commonly sent to the calmecac, where they studied history, religion, astronomy, law, rhetoric, and administration.

Pipiltin should not be confused with macehualtin, the broad class of commoners. A commoner could sometimes gain prestige or even elevated status through exceptional military service, so Aztec society was not entirely immobile. Nevertheless, the pipiltin remained the recognized hereditary noble class, and rulers were generally selected from elite lineages.

The term pilli could also appear in more specific noble titles, including words identifying the son of a ruler or another high-ranking lord. Pipiltin is therefore the precise answer for the class as a whole.