In a volcanic eruption, lava, tephra (volcanic bombs, lapilli, and ash), and various gases are expelled from a volcanic vent or fissure. While many eruptions only pose dangers to the immediately surrounding area, Earth's largest eruptions can have a major regional or even global impact, with some affecting the climate and contributing to mass extinctions.^[1][2] Volcanic eruptions can generally be characterized as either explosive eruptions, sudden ejections of rock and ash, or effusive eruptions, relatively gentle outpourings of lava.^[3] A separate list is given below for each type.

All of the eruptions listed below have produced at least 1,000 km³ (240 cu mi) of lava and tephra; for explosive eruptions, this corresponds to a Volcanic Explosivity Index (or VEI) of 8.^[4] They are at least a thousand times larger than the 1980 eruption of Mount St. Helens which produced only 1 km³ (0.2 cu mi) of material,^[5] and at least six times larger than the 1815 eruption of Mount Tambora, the largest eruption in recent history, which produced 160 km³ (38 cu mi) of volcanic deposits.

There have probably been many such eruptions during Earth's history beyond those shown in these lists. However erosion and plate tectonics have taken their toll, and many eruptions have not left enough evidence for geologists to establish their size. Even for the eruptions listed here, estimates of the volume erupted can be subject to considerable uncertainty.^[6]