The Toltec people (also known as Tolteca or Tolteca-Chichimeca) and their legendary city (or cities) called Tula or Tollan constitute one of the most controversial and poorly understood cultural traditions in ancient Mesoamerica. In Nahua historical texts written by Central Mexican peoples shortly after the Spanish conquest, the word “Toltec” frequently is used to denote wise, highly civilized people and, more specifically, people who lived in cities. The name of the Toltec capital, Tollan, metaphorically means city—“Place of Rushes,” or “Place of Reeds,” or “Place where people are as common as reeds.” The concept of cities being “places of reeds” probably is very old in Mesoamerica. Linda Schele and Peter Mathews suggest that this metaphor started with the Formative-period Olmec, whose swampy Gulf Coast homeland could have been the original “place of reeds,” and the Maya probably called Teotihuacan “Cattail Reed” in hieroglyphic texts.

Despite the antiquity of the concepts of Tollan and the Toltecs, most scholars agree that the major indigenous Central Mexican chronicles of the Toltecs concern a people who existed five to six centuries before the Spanish conquest and whose principal capital probably corresponds to the ruins at Tula, Hidalgo, about eighty kilometers (50 miles) north of Mexico City. Archaeological investigations have shown, by about 800 CE, that Tula already constituted a city covering several square kilometers. This city was a synthesis of two cultural traditions: the preceding urban tradition in the Basin of Mexico centered on Classic Teotihuacan, and immigrant peoples from the northern Mesoamerican periphery (probably the Bajío and the Zacatecas-Jalisco border area) who may have been the “Tolteca-Chichimeca” mentioned in chronicles as northerners who helped found Tula.

After the collapse of Teotihuacan in the seventh or eighth centuries CE, Toltec Tula was the first state to integrate peoples of Mexico and Central America into a new cultural system. This transformation of key institutions in Mesoamerican civilization by the Toltec involved several interrelated processes: the settlement of Toltec groups speaking Nahuatl (or sometimes Otomí) in regions outside Central Mexico; the founding in many areas of royal dynasties which claimed Toltec origins, though not all of them had kinship ties with Tula's nobility; the expansion of trade systems, partially centered on Tula, which extended from Costa Rica and Nicaragua to the U.S. Southwest; and significant changes in the religions of some peoples as a result of contact with the Toltecs, who introduced Nahua gods to non-Nahua groups and spread the epic of the man-god Quetzalcoatl among peoples in Central Mexico, Yucatán, Highland Guatemala, and other areas.

Tula probably possessed an empire which included much of Central Mexico, along with areas of the Bajío, the Gulf Coast, Yucatán, and the Pacific coast of Chiapas and Guatemala. The Toltecs probably controlled parts of Michoacán and the Huasteca which the Aztecs never conquered, and the multifaceted Toltec presence at Chichén Itzá in Yucatán has no Aztec correlate during the Late Postclassic period. Tula probably had fewer provinces than Tenochtitlan, but during the Early Postclassic (900–1200 CE) Tula's cultural influence extended over much of Mesoamerica.