Tlatelolco is an archaeological excavation site in Mexico City, Mexico where remains of the pre-Columbian city-state of the same name have been found. It is centered on the Plaza de las Tres Culturas. On one side of the square is this excavated Tlatelolco site, on a second is the oldest European school of higher learning in the Americas called the Colegio de Santa Cruz de Tlatelolco, and on the third stands a mid-20th-century modern office complex, formerly housing the Mexican Foreign Ministry, and since 2005 used as the Centro Cultural Universitario of UNAM (National University of Mexico).

Tlatelolco was founded in 1338, thirteen years later than Tenochtitlan. At the main temple of Tlatelolco, archeologists recently discovered a pyramid within the visible temple; the pyramid is more than 700 years old. This indicates that the site is older than previously thought, according to the Instituto Nacional de Antropología e Historia (National Institute of Anthropology and History; INAH). Because this pyramid has design features similar to pyramids found in Tenayuca and Tenochtitlan, this site may prove to be the first mixed Aztec and Tlatelolca construction found in Mexico.