Mount Pinatubo is an active stratovolcano in the Zambales Mountains, located on the tripoint boundary of the Philippine provinces of Zambales, Tarlac and Pampanga, all in Central Luzon on the northern island of Luzon.

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Its eruptive history was unknown to most before the pre-eruption volcanic activities of 1991, just before June. Pinatubo was heavily eroded inconspicuous and obscured from view. It was covered with dense forest which supported a population of several thousand indigenous Aetas.

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The volcano's Ultra Plinian eruption on June 15, 1991, produced the second-largest terrestrial eruption of the 20th century after the 1912 eruption of Novarupta in the Alaska Peninsula.

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The effects of the eruption were felt worldwide. It ejected roughly 10,000,000,000 tonnes of magma, and 20,000,000 tonnes (22,000,000 short tons) of Sulfur dioxide, bringing vast quantities of minerals and toxic metals to the surface environment. It injected more particulate into the stratosphere than any eruption since Krakatoa in 1883.