Lake Pinatubo (Filipino: Lawa ng Pinatubo) is the summit crater lake of Mount Pinatubo formed after its climactic eruption on June 15, 1991. The lake is located near the boundaries of Pampanga, Tarlac and Zambales provinces in the Philippines and is the deepest lake in the country at 600 m (2,000 ft). It is about 90 km (56 mi) northwest of the capital city of Manila.

Mount Pinatubo's volcanic activity has followed a cycle: centuries of repose terminated by a caldera-forming eruption with largepyroclastic flows; a post-eruption aftermath of rain-triggered lahars in surrounding drainages and dome-building that fills the caldera; and then another long quiescent period. During and after the eruptions, lahars descending along volcano channels may block tributaries from watersheds beyond Pinatubo, creating natural lakes.^[3] Geophysical evidence shows that there were at least two ancient lakes in the Mapanuepe River valley in the southwestern part of the volcano.