Coatepeque Caldera (Nawat: cōātepēc, "at the snake hill") is a volcanic caldera in El Salvador in Central America. The caldera was formed during a series of rhyolitic explosive eruptions from a group of stratovolcanoes between about 72,000 and 57,000 years ago. Since then, basaltic cinder cones and lava flows formed near the west edge of the caldera, and six rhyodacitic lava domes have formed. The youngest dome, Cerro Pacho, formed after 8000 BC.

Lake Coatepeque (Lago de Coatepeque) is a large crater lake in the east part of the Coatepeque Caldera. It is in Coatepeque municipality, Santa Ana, El Salvador. There are hot springs near the lake margins. At 26 square kilometres (10 sq mi), it is one of the largest lakes in El Salvador. In the lake is the island of Teopan, which was a Mayan site of some importance.

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Lake Coatepeque is also known to change colors from blue to turquoise. According to authorities of the, this is a cyclical phenomenon that occurs from time to time. The color change has happened in 1998, 2006, 2012, 2016, 2017, 2018, and 2019.

• List of volcanoes in El Salvador

• "Coatepeque Caldera". Global Volcanism Program. Smithsonian Institution.