Bulmer Cavern, Cave system in Tasman District, New Zealand

Bulmer Cavern runs 74.3 km through Mount Owen in Kahurangi National Park, making it New Zealand's longest cave system. Its passages and chambers lie beneath the mountain, and the system reaches a depth of 749 m, the third deepest in the country.

John Patterson discovered Bulmer Cavern on New Year's Day 1985 by dropping a rock down a shaft and counting the seconds until it hit the bottom. Members of the New Zealand Speleological Society explored and surveyed the system that same year. It now ranks as the country's longest cave, running 74.3 km through Mount Owen, and its deepest point lies 749 m below the surface.

The cave network holds particular importance for New Zealand speleologists who document and study its geological characteristics and underground formations.

Bulmer Cavern runs through Mount Owen in Kahurangi National Park, reached on foot from the Bulmer area near the Owen River. Entry is by rope down vertical shafts, so cavers need SRT rigging skills and a permit from the New Zealand Speleological Society. Trips last several days; the 1998 rescue of an injured caver took 80 people to carry out.

John Patterson found the entrance on New Year's Day 1985 by dropping a rock down the shaft and counting the seconds until it hit bottom. The 1998 rescue of a caver with a broken jaw deep inside took 80 cavers several days to complete.