Billy Mitchell is a pyroclastic shield in the central part of the island of Bougainville, just north-east of the Bagana Volcano in Papua New Guinea. It is a small pyroclastic shield truncated by a 2 km wide caldera filled by a crater lake. It is named after Billy Mitchell, a 20th-century United States Army general who is regarded as the father of the United States Air Force.

The last two major eruptions were in 1580 AD ± 20 years and about 1030 AD. They were among the largest Holocene eruptions in Papua New Guinea. Both were explosive eruptions with a Volcanic Explosivity Index of at least 5. The 1580 AD ± 20 years eruption produced pyroclastic flows and probably formed its caldera. The ignimbrite deposit from that eruption, which had a VEI of 6, extends 22 kilometres (14 mi) from the caldera to the coast, and its volume is around 10 cubic kilometres (2.4 cu mi).

Billy Mitchell caldera lake is about 1,013 m above sea level, has total surface area 3 km (1.2 sq mi), and the maximum depth approximately 88.3 m. The only fish species in the lake is the eel Anguilla megastoma. Billy Mitchell lake drains into the Tekan River.

• List of volcanoes in Papua New Guinea
• Mount Billy Mitchell (Chugach Mountains)
• Timeline of volcanism on Earth

• Photo of the Billy Mitchell Crater Lake
• "Billy Mitchell". Global Volcanism Program. Smithsonian Institution. Retrieved 2011-11-08.