Suwa Cave, Natural monument cave in Okayama Prefecture, Japan.

Suwa Cave is a protected natural cave in Okayama Prefecture featuring multiple chambers filled with limestone formations. Its interior displays geological patterns created over millions of years through natural processes.

Suwa Cave was surveyed in 1970 by Ehime University, which explored about 900 m up to the second sump, a water-filled passage. In 1998 divers pushed beyond that sump and mapped the cave to roughly 1,750 m at the fourth sump. The sources record no monument designation.

The stream flowing from the cave mouth empties into the Bitchū River, and the sound of its falling water was chosen for the Environment Agency's 1996 list of 100 Soundscapes of Japan. The cave lies in the former Kawakami village area of Maniwa, near a firefly park whose parking area serves cave visitors.

The cave is reached by car about 10 minutes from the Hokubo interchange of the Chugoku Expressway, using the parking lot of the hotaru park just before it. By public transport, take a bus from Takahashi Bus Center toward Ochi Station and get off at the Azai stop, then walk about 10 minutes. As of 2024 entry is prohibited just inside the cave mouth because the steel walkway has deteriorated.

The sound of water flowing from the cave mouth into the Bitchū River was chosen in 1996 by the Environment Agency as one of Japan's 100 Soundscapes. Inside, a steel walkway has deteriorated and broken; as of 2024 entry is barred just past the cave mouth.