The city is thought to have been established around 100 BCE and continued to be built until about 250 CE. The city may have lasted until sometime between the 7th and 8th centuries CE. At its zenith, perhaps in the first half of the 1st millennium CE, Teotihuacan was the largest city in the pre-Columbian Americas. At this time it may have had more than 200,000 inhabitants, placing it among the largest cities of the world in this period. Teotihuacan was even home to multi-floor apartment compounds built to accommodate this large population. The civilization and cultural complex associated with the site is also referred to as Teotihuacan or Teotihuacano.

Although it is a subject of debate whether Teotihuacan was the center of a state empire, its influence throughout Mesoamerica is well documented; evidence of Teotihuacano presence can be seen at numerous sites in Veracruz and the Maya region. The Aztecs may have been influenced by this city. The ethnicity of the inhabitants of Teotihuacan is also a subject of debate. Possible candidates are the Nahua, Otomi or Totonac ethnic groups. Scholars have also suggested that Teotihuacan was a multiethnic state.

The city and the archaeological site are located in what is now the San Juan Teotihuacán municipality in the State of México, Mexico, approximately 40 kilometres (25 mi) northeast of Mexico City. The site covers a total surface area of 83 km² and was designated a UNESCO World Heritage Site in 1987. It is one of the most visited archaeological sites in Mexico.