The Lacandon Jungle (Spanish: Selva Lacandona) is an area of rainforest which stretches from Chiapas, Mexico, into Guatemala. The heart of this rainforest is located in the Montes Azules Biosphere Reserve in Chiapas near the border with Guatemala in the Montañas del Oriente region of the state. Although much of the jungle outside the reserve has been cleared, the Lacandon is still one of the largest montane rainforests in Mexico. It contains 1,500 tree species, 33% of all Mexican bird species, 25% of all Mexican animal species, 56% of all Mexican diurnal butterflies and 16% of all Mexico's fish species.
The Lacandon in Chiapas is also home to a number of important Mayan archaeological sites including Palenque, Yaxchilan and Bonampak, with numerous smaller sites which remain partially or fully unexcavated. This rainforest, especially the area inside the Biosphere Reserve, is a source of political tension, pitting the EZLN or Zapatistas and their indigenous allies who want to farm the land against international environmental groups and the Lacandon Maya, the original indigenous group of the area and the one that holds the title to most of the lands in the Montes Azules.