Mount Unzen (jp: 雲仙岳 Unzendake) is an active volcanic complex of several overlapping stratovolcanoes near the city of Shimabara, Nagasaki Prefecture, on the island of Kyūshū, Japan’s southernmost main island.
In 1792, the collapse of one of its several lava domes triggered a tsunami that killed about 15,000 people in Japan’s worst-ever volcanic disaster. The volcano was most recently active from 1990 to 1995, and a large eruption in 1991 generated a pyroclastic flow that killed 44 people, including three volcanologists.
Currently its highest peaks are Fugendake (普賢岳) at 1,359 meters and Heisei Shinzan (平成新山) at 1,486 meters. The latter emerged during the eruptions of the early, eponymous Heisei era (1989–).