Mount Yasur, Active volcano on Tanna Island, Vanuatu

Mount Yasur is a 361 m stratovolcano on Tanna Island, Vanuatu, whose largely unvegetated pyroclastic cone rises near Sulphur Bay, northeast of Mount Tukosmera. Its nearly circular summit crater, about 400 m across, holds several vents; the German source gives the main crater Vulki Mulki a diameter of roughly 300 m and a depth of about 150 m with five vents. Visitors look down into the crater from the rim, not inside it, as ash plumes and lava fountains rise from the active southern vent.

Captain James Cook documented the volcano for the first time in 1774 when he saw the glowing fire and ongoing eruptions from his ship. Since then the mountain has shown fiery activity without interruption and counts among the permanently active fire mountains of the world.

The volcano is sacred to the John Frum cargo cult, whose members revere a deified messenger believed to live inside Mount Yasur with his countrymen. Sulphur Bay village, the movement's centre, claims the mountain as its territory. The name Yasur comes from the Kwamera word iasur, meaning "volcano".

The Vanuatu Geo-Hazards Observatory operates a five-level alert system that informs about current danger and helps decide whether a visit is safe. Conditions can change quickly, so check the current status before heading to the summit.

The IUGS listed the Yasur–Yenkahe volcanic complex, not the volcano alone, among its 100 geological heritage sites in October 2022, citing an 800-year-long eruption and the nickname "lighthouse of the Pacific". From 2005 a volcanic postbox stood below the crater, the only one of its kind in the world; by 2024 it no longer existed.