The Nahuas (/ˈnɑːwɑːz/ NAH-wahz) are a Uto-Nahuan ethnic group and one of the Indigenous people of Mexico, with Nahua minorities also in El Salvador, Guatemala, Honduras, Nicaragua, and Costa Rica. They comprise the largest Indigenous group in Mexico, as well as the largest population out of any North American Indigenous people group who are native speakers of their respective Indigenous language. Amongst the Nahua, this is Nahuatl. When ranked amongst all Indigenous languages across the Americas, Nahuas list third after speakers of Guaraní and Quechua.

The Mexica (Aztecs) are of Nahua ethnicity, as are their historical enemies and allies of the Spaniards: the Tlaxcallans (Tlaxcaltecs). The Toltecs which predated both groups are often thought to have been Nahua as well. However, in the pre-Columbian period Nahuas were subdivided into many groups that did not necessarily share a common identity.

Their Nahuan languages, or Nahuatl, consist of many variants, several of which are mutually intelligible. About 1.5 million Nahuas speak Nahuatl and another million speak only Spanish. Fewer than 100 native speakers of Nawat remain in El Salvador.

It is suggested that the Nahua peoples originated near Aridoamerica, in regions of the present day Mexican states of Durango and Nayarit or the Bajío region. They split off from the other Uto-Aztecan speaking peoples and migrated into central Mexico around 500 CE. The Nahua then settled in and around the Basin of Mexico and spread out to become the dominant people in central Mexico. However, Nahuatl-speaking populations were present in smaller populations throughout Mesoamerica.

The name Nahua is derived from the Nahuatl word-root nāhua- [ˈnaːwa-], which generally means "audible, intelligible, clear" with different derivations including "language" (hence nāhuat(i) [ˈnaːwat(i)] "to speak clearly" and nāhuatl [ˈnaːwat͡ɬ] both "something that makes an agreeble sound" and "someone who speaks well or speak one's own language"). It was used in contrast with popoloca [popoˈloka], "to speak unintelligibly" or "speak a foreign language". Another, related term is Nāhuatlācatl [naːwaˈt͡ɬaːkat͡ɬ] (singular) or Nāhuatlācah [naːwaˈt͡ɬaːkaʔ] (plural) literally "Nahuatl-speaking people".

The Nahuas are also sometimes referred to as Aztecs. Using this term for the Nahuas has generally fallen out of favor in scholarship, though it is still used for the Aztec Empire. They have also been called Mēxihcatl [meːˈʃiʔkat͡ɬ] (singular), Mēxihcah [meːˈʃiʔkaʔ] (plural) or in Spanish Mexicano(s) [mexiˈkano(s)] "Mexicans", after the Mexica, the Nahua tribe which founded the Aztec Empire.

The Mexican government does not categorize its citizens by ethnicity, but only by language. Statistical information recorded about the Nahua deals only with speakers of the Nahuatl language, although unknown numbers of people of Nahua ethnicity have abandoned the language and now speak only Spanish. Other Nahuas, though bilingual in Nahuatl and Spanish, seek to avoid widespread anti-Indigenous discrimination by declining to self-identify as Nahua in INEGI's decennial census. Nor does the census count as Indigenous children under 5 (estimated to be 11–12% of the Indigenous population). An INI-Conepo report indicates the Mexican Indigenous population is nearly 250% greater than that reported by INEGI.

As of 2020, Nahuatl is spoken across Mexico by an estimated 1.6 million people, including 111,797 monolingual speakers. This is an increase from 1.4 million people speakers total but a decrease from 190,000 monolingual speakers in 2000. The state of Guerrero had the highest ratio of monolingual Nahuatl speakers, calculated at 24.8%, based on 2000 census figures. The proportion of monolinguals for most other states is less than 5%.