Tlacopan (meaning "florid plant on flat ground"), also called Tacuba, was a Pre-Columbian Mesoamerican city-state situated on the western shore of Lake Texcoco on the site of today's neighborhood of Tacuba in Mexico City.
Near Tlacopan was city of Tiliuhcan.
Tlacopan sided with Tenochtitlan and Texcoco in their conquest of Azcapotzalco, becoming a member of the Triple Alliance which formed the nucleus of the Aztec Empire. The ruler of Tlacopan, Totoquihuaztli, then took the title Tepaneca tecuhtli, "Lord of the Tepanecs" (probably taken from the rulers of Azcapotzalco). Tlacopan was to remain a junior partner in the alliance, receiving only a fifth of the tribute gained from joint campaigns with its more powerful allies.
The Triple Alliance ended with the Spanish conquest of Mexico by Hernán Cortés and native allies in 1521. Over the centuries, Mexico City expanded to include the former site of Tlacopan, today's neighborhood of Tacuba in the Mexico City borough of Miguel Hidalgo.