Mount Bromo (left) with an eruption Semeru volcano in the back

Semeru, or Mount Semeru (Indonesian: Gunung Semeru), is a volcano located in East Java, Indonesia. It is the highest mountain on the island of Java. The stratovolcano is also known as Mahameru, meaning 'The Great Mountain. The name derived from Hindu-Buddhist mythical mountain of Meru or Sumeru, the abode of gods.

Bromo Tengger Semeru National Park is located in East Java, Indonesia, to the east of Malang and to the southeast of Surabaya, the capital of East Java. It is the only conservation area in Indonesia that has a sand sea, the Tengger Sand Sea (Indonesian: Laut Pasir Tengger), across which is the caldera of an ancient volcano (Tengger) from which four new volcanic cones have emerged. This unique feature covers a total area of 5,250 hectares at an altitude of about 2,100 m. The massif also contains the highest mountain in Java, Mount Semeru (3,676 m), four lakes and 50 rivers.

The Tengger Sand Sea has been protected since 1919. The Bromo Tengger Semeru National Park was declared a national park in 1982.