Naachtun is an archaeological site of the pre-Columbian Maya civilization, situated at the northeastern perimeter of the Mirador Basin region in the southern Maya lowlands, now in the modern-day Department of El Petén, northern Guatemala. Naachtun was a major center of the region by the late Formative (or Pre-Classic) Period, and was one of the few Formative Period Mirador Basin centers which continued to flourish into the succeeding Classic period.
Situated in one of the areas most remote from contemporary settlements, the site was first rediscovered and documented in 1922 by the American archaeologist and Mayanist scholar, Sylvanus Morley. The name Naachtun was given to the site by Morley, taken from a Mayan construction glossed as "distant stones", in recognition of its remoteness. Its ancient name was Masuul, and it was in the middle of the Classic Maya cities. The site is being investigated by the Calgary University, where they have found that the site served as a link between Tikal and Calakmul, that were the superpowers in the Classic, and in constant wars between them, perhaps using Massul as a "Neutral Talk Place". A carved stela with the "Lady of Tikal" has been recently found there. The site is quite large, with several Pyramid temples and Acropolis, linked with sacbeob, as well as 2 ballcourts.