Mount Rinjani or Gunung Rinjani is an active volcano in Indonesia on the island of Lombok. Administratively the mountain is in the Regency of North Lombok, West Nusa Tenggara (Indonesian: Nusa Tenggara Barat, NTB). It rises to 3,726 metres (12,224 ft), making it the second highest volcano in Indonesia.
On the top of the volcano is a 6 kilometres (3.7 mi) by 8.5 kilometres (5.3 mi) caldera, which is filled partially by the crater lake known as Segara Anak (Child of the Sea). This lake is approximately 2,000 metres (6,600 ft) above sea level and estimated to be about 200 metres (660 ft) deep; the caldera also contains hot springs.
A massive eruption of Rinjani in 1258 CE may have triggered the Little Ice Age.