Fourpeaked Mountain, Stratovolcano in Katmai National Park, Alaska, United States.

Fourpeaked Mountain is an active stratovolcano in Katmai National Park and Preserve, Alaska, within the Aleutian volcanic arc. It reaches 2,105 metres above sea level and is almost entirely covered by Fourpeaked Glacier, so its summit peaks and flanks show mostly ice and snow rather than bare rock.

The volcano lay dormant for about 10,000 years before awakening in September 2006, when large steam plumes became visible from Homer across Cook Inlet. This marked its first major sign of activity after a long period of rest.

The name Fourpeaked refers to the four summit peaks visible above Fourpeaked Glacier, which covers nearly the whole cone. The 2006 steam plumes were spotted by pilots and civilians as far off as Homer, across Cook Inlet, and air sampling by the Alaska Volcano Observatory confirmed volcanic gases venting near the summit.

Fourpeaked Mountain stands in Katmai National Park and Preserve, on the Alaska Peninsula west of Cook Inlet, not in the Aleutian Range near Kodiak. There are no roads or trails to the volcano; access is by floatplane or boat, and the summit and flanks are almost entirely covered by Fourpeaked Glacier, so crampons and glacier travel skills are needed. Flights and landings depend on weather and volcanic alert status.

The entire volcanic structure lies buried beneath Fourpeaked Glacier, creating an extraordinary combination of thermal heat beneath permanent ice. Scientists track the heat sources hidden under the ice through remote sensing and seismic monitoring.