Kelimutu ([kəliˈmutu]) is a volcano, close to the small town of Moni about 50 km to the east of Ende, Indonesia in central Flores Island of Indonesia.
The volcano contains three striking summit crater lakes of varying colors. Tiwu Ata Mbupu (Lake of Old People) is usually blue and is the westernmost of the three lakes. The other two lakes, Tiwu Nuwa Muri Koo Fai (Lake of Young Men and Maidens) and Tiwu Ata Polo (Bewitched or Enchanted Lake) are separated by a shared crater wall and are typically green or red respectively. The lake colors vary on a periodic basis. Subaqueous fumaroles are the probable cause of active upwelling that occurs at the two eastern lakes.
The lakes have been a source of minor phreatic eruptions in historical time. The summit of the compound 1639-m-high Kelimutu volcano is elongated two km in a WNW-ESE direction; the older cones of Kelido and Kelibara are located respectively three km to the north and two km to the south. The scenic lakes are a popular tourist destination.
Kelimutu is also of interest to geologists because the three lakes have different colors yet are at the crest of the same volcano. According to the local officer at Kelimutu National Park, the colour changes as a result of chemical reactions resulting from the minerals contained in the lake perhaps triggered by volcano gas activity. Kawah Putih lake in West Java, south of Bandung, is another crater lake in Indonesia with some similarities to the lakes at Kelimutu.