The Aztec Empire or the Triple Alliance was an alliance of three Nahua city-states: Mexico-Tenochtitlan, Tetzcoco, and Tlacopan. These three city-states ruled that area in and around the Valley of Mexico from 1428 until the combined forces of the Spanish conquistadores and their native allies who ruled under Hernán Cortés defeated them in 1521.

The Nahuas are a group of the Indigenous people of Mexico, El Salvador, Guatemala, Honduras, Nicaragua, and Costa Rica. They comprise the largest indigenous group in Mexico and El Salvador. They are a Mesoamerican ethnicity. The Mexica (Aztecs) are of Nahua ethnicity, as are their historical enemies, the Tlaxcallans (Tlaxcaltecs), and the Toltecs which predated both groups are often thought to have been as well. However, in the pre-Columbian period Nahuas were subdivided into many groups that did not necessarily share a common identity.