Nahuatl (Nahuatl pronunciation: [ˈnaːwatɬ] ( listen), with stress on the first syllable) is a group of related languages and dialects of the Nahuan (traditionally called "Aztecan") branch of the Uto-Aztecan language family. Altogether they are spoken by an estimated 1.5 million Nahua people, most of whom live in Central Mexico. All Nahuan languages are indigenous to Mesoamerica.

Nahuatl has been spoken in Central Mexico since at least the 7th century AD. It was the language of the Aztecs, who dominated what is now central Mexico during the Late Postclassic period of Mesoamerican chronology. During the preceding century and a half, the expansion and influence of the Aztec Empire had led to the variety spoken by the residents of Tenochtitlan becoming a prestige language in Mesoamerica. With the introduction of the Latin alphabet, Nahuatl also became a literary language and many chronicles, grammars, works of poetry, administrative documents and codices were written in the 16th and 17th centuries. This early literary language based on the Tenochtitlan variety has been labeled Classical Nahuatl and is among the most studied and best documented languages of the Americas.