The Erdene Zuu Monastery (Mongolian: Эрдэнэ Зуу, Chinese: 額爾德尼召) is probably the most ancient surviving Buddhist monastery in Mongolia. It is in Övörkhangai Province, near the town of Kharkhorin and adjacent to the ancient city of Karakorum. It is part of the World Heritage Site entitled Orkhon Valley Cultural Landscape. The Chinese name of Erdene Zuu Monastery is Guangxian Temple (光顯寺).
The Erdene Zuu monastery was built in 1585 by Abtai Sain Khan, upon the (second) introduction of Tibetan Buddhism into Mongolia. Stones from the ruins of Karakorum were used in construction. It is surrounded by a wall featuring 100 stupas. The number 108, being a sacred number in Buddhism, and the number of beads in a Buddhist rosary, was probably envisioned, but never achieved. The monastery temples' wall were painted, and the Chinese-style roof was covered with green tiles. The monastery was damaged by warfare in the 1680s, but was rebuilt in the 18th century and by 1872 had a full 62 temples inside.
In 1939 the Communist leader Khorloogiin Choibalsan had the monastery ruined, as part of a purge that obliterated hundreds of monasteries in Mongolia and killed over ten thousand monks. Three small temples and the external wall with the stupas remained; the temples became museums in 1947. They say that this part of the monastery was spared destruction on account of Joseph Stalin's pressure. One researcher claims that Stalin's pressure was connected to the short visit of US vice president Henry A. Wallace's delegation to Mongolia in 1944.
Erdene Zuu was allowed to exist as a museum only; the only functioning monastery in Mongolia was Gandantegchinlen Khiid Monastery in the capital, Ulaanbaatar. However, after the fall of Communism in Mongolia in 1990, the monastery was turned over to the lamas and Erdene Zuu again became a place of worship. Today Erdene Zuu remains an active Buddhist monastery as well as a museum that is open to tourists.
On a hill outside the monastery sits a stone phallus. The phallus is said to restrain the sexual impulses of the monks and ensure their good behavior.