The Aztec people were certain ethnic groups of central Mexico, particularly those groups who spoke the Nathuatl language and who dominated large parts of Mesoamerica in the 14th, 15th and 16th centuries, a period referred to as the late post-classic period in Mesoamerican chronology.
Often the term "Aztec" refers exclusively to the Mexica people of Tenochtitlan, situated on an island in Lake Texococo, who referred to themselves as Mexica Tenochca or Colhua-Mexica. Sometimes the term also includes the inhabitants of Tenochtitlan's two principal allied city-states, the Acolhuas of Texococo and the Tepanecs of Tlacopan, who together with the Mexica formed the Aztec Triple Alliance which has also become known as the "Aztec Empire".
In other contexts, Aztec may refer to all the various city states and their peoples, who shared large parts of their ethnic history as well as many important cultural traits with the Mexica, Acolhua and Tepanecs, and who like them, also spoke the Nahuatl language. In this meaning it is possible to talk about an Aztec civilization including all the particular cultural patterns common for the Nahuatl speaking peoples of the late postclassic period in Mesoamerica.
From the 13th century Valley of Mexico was the core of Aztec civilization: here the capital of the Aztec Triple Alliance, the city of Tenochtitlan, was built upon raised islets in Lake Techoco. The Triple Alliance formed its tributary empire expanding its political hegemony far beyond the Valley of Mexico, conquering other city states throughout Mesoamerica. At its pinnacle Aztec culture had rich and complex mythological and religious traditions, as well as reaching remarkable architectural and artistic accomplishments.
In 1521, in what is probably the most widely known episode in theSpanish colonization of the Americas, Hernán Cortés, along with a large number of Nahuatl speaking indigenous allies, conquered Tenochtitlan and defeated the Aztec Triple Alliance under the leadership of Hueyi Tlatoani Moctezuma II; In the series of events often referred to as "The fall of the Aztec Empire". Subsequently the Spanish founded the new settlement of Mexico city on the site of the ruined Aztec capital.