The Aztecs is a term used for certain Pre-Columbian Mesoamerican peoples of Mexico. Sometimes it refers exclusively to the Mexica people, founders of the island city Tenochtitlan. Sometimes it also includes their two principal allies, the people of Tetzcoco and Tlacopan, with whom they built an extensive empire in the late Postclassic period in the 14th, 15th and 16th centuries. And sometimes it is used about all the Nahua peoples.
The nucleus of the Aztec Empire was the Valley of Mexico, where the capital of the Aztec Triple Alliance, the city of Tenochtitlan was built upon raised islets in Lake Texcoco. After the 1521 conquest of Tenochtitlan by Spanish forces and their allies which brought about the effective end of Aztec dominion, the Spanish founded the new settlement of Mexico City on the site of the now-ruined Aztec capital. The capital of the modern-day nation of Mexico, the greater metropolitan area of Mexico City now covers much of the Valley of Mexico and the now-drained Lake of Texcoco.
Aztec culture had rich and complex mythological and religious traditions. For Europeans, the most striking element of the Aztec culture was the practice of human sacrifice which was conducted throughout Mesoamerica prior to the Spanish conquest.
In what is probably the most widely known episode in the Spanish colonization of the Americas, Hernán Cortés conquered the Aztecs in 1521 thus immortalizing himself and the Aztec Hueyi Tlatoani, Moctezuma II (Motecuhzoma II).
The Aztecs spoke Classical Nahuatl. Although some contemporary Nahuatl speakers identify themselves as Aztecs, the word is normally only used as a historical term referring to the empire of the Mexicas. This article deals with the historical Aztec civilization, not with modern-day Nahuatl speakers.