Kazumura Cave, Lava tube cave system in Hilo, United States.

Kazumura Cave is a lava tube system extending beneath the eastern slope of Kilauea volcano, ranking among the world's longest continuous volcanic passages. The cavern displays basalt walls and natural formations created by flowing lava over many centuries.

Kazumura Cave lies in the ʻAilāʻau lava flow, which originated from Kīlauea Iki Crater about 500 years ago. In 1966 one entrance was designated a fallout shelter, and in the early 1970s Francis Howarth's discovery of the troglobitic moth Schrankia howarthi brought cavers' attention. A 1981 British expedition surveyed 7.27 miles. Kevin Allred and Mike Meyer joined Upper and Old Kazumura, and Sexton and Olaʻa caves were linked by 1995; a year of surveying in 1993 confirmed it as the world's longest lava tube.

The cave lies on private land, and the Kazumura Cave Atlas lists 101 entrances, all on private property; under Hawaiʻi law landowners must be asked before entering any lava tube on their land. At least one landowner has run paid adventure tours through his section of the cave since 2016. The name comes from the land where it opens, and the cave is known in caving circles through the Allreds' atlas.

All 101 entrances lie on private land, so ask the landowner before entering; at least one owner runs paid adventure tours through his section. Access is by arrangement, and the cave is only lightly developed for visitors. Expect uneven lava floor and passages that require crawling in places.

The cave's endemic fauna is easy to miss: a blind planthopper (Oliarus polyphemus) feeds on the roots of native ʻōhiʻa trees, alongside a cave cricket, Caconemobius varius, two Schrankia moth species and Cavaticovelia aaa, a cave-adapted water treader. These arthropods live mainly in cooling cracks in the surrounding pahoehoe lava and only sometimes move into the passages.