Aztec culture is generally grouped with the cultural complex known as the nahuas, because of the common language they shared. According to legend, the various groups who were to become the Aztecs arrived from the north into the Anahuac valley around Lake Texcoco. The location of this valley and lake of destination is clear – it is the heart of modern Mexico City – but little can be known with certainty about the origin of the Aztecs. 

Tenochtitlan – Aztec capital on an artificial island, which today is Mexico CityIn the legend, the ancestors of the Aztecs came from a place in the north called Aztlán, the last of seven nahuatlacas (Nahuatl-speaking tribes) to make the journey southward. The Aztecs were said to be guided by their god Huitzilopochtli, meaning "Left-handed Hummingbird". When they arrived at an island in the lake, they saw an eagle eating a snake while perched on a nopal cactus, a vision that fulfilled a prophecy telling them that they should found their new home on that spot. The Aztecs built their city of Tenochtitlan on that site, building a great artificial island, which today is in the center of Mexico City. This legendary vision is pictured on the Mexican flag. 

According to legend, when the Aztecs arrived in the Anahuac valley around Lake Texcoco, they were considered by the other groups as the least civilized of all, but the Aztecs decided to learn, and they took all they could from other peoples, especially from the ancient Toltecs (whom they seem to have partially confused with the more ancient civilization of the Teotihuacanos). To the Aztecs, the Toltecs were the originators of all culture; "Toltecayotl" was a synonym for culture. Aztec legends identify the Toltecs and the cult of Quetzalcoatl with the mythical city of Tollan, which they also seem to have identified with the more ancient Teotihuacan. 

Because the Aztecs combined several traditions with their own earlier traditions, they had several creation myths; one of these describes four great ages preceding the present world, each of which ended in a catastrophe. Our age – Nahui-Ollin, the fifth age, or fifth creation – escaped destruction due to the sacrifice of a god (Nanahuatl, "full of sores", the smallest and humblest of the gods) who was transformed into the Sun. This myth is associated with the ancient city of Teotihuacan, which was already abandoned and destroyed when the Aztecs arrived. Another myth describes the earth as a creation of the twin gods Tezcatlipoca and Quetzalcoatl. Tezcatlipoca lost his foot in the process of creating the world and all representations of these gods show him without a foot and with a bone exposed. Quetzalcoatl is also called "White Tezcatlipoca".