Udone-shima (鵜渡根島) is a volcanic, deserted island located in the Philippine Sea approximately 150 kilometres (93 mi) south of Tokyo in between Toshima and Nii-jima, in the northern portion of the Izu archipelago, Japan.

The island is the remnant of an andesite lava dome with sheer sides, the only visible portion of a submarine volcanic caldera. The above sea-level portion has a surface area of approximately 0.4 square kilometers, with a summit height of 210 metres (690 ft). The main island is surrounded by a number of rocks.

Despite its small size, the island was formerly inhabited during the Meiji period by a small community of fishermen who also engaged in sericulture. A small Shinto shrine still exists on the island.

This island shares many similarities in its biodiversity in common with neighboring islands such as Nii-jima. Being surrounded by rough sea, vicinity to the island is rather difficult to visit in fact, and this made the natural environments of the islands and nearby atolls protected. Indo-Pacific bottlenose dolphins that newly inhabited around Udone-shima as their residential range has been expanded wider even onto Honshu coasts. Larger sharks inhabit the area. Historically, a breeding colony of now-extinct Japanese sea lions once existed on the island as well.

• Izu Islands
• Desert island
• List of islands

Wikimedia Commons has media related to Utoneshima.

• Udone Jima at Quaternary Volcanoes of Japan
• Entry at Oceandots.com at the Wayback Machine (archived December 23, 2010)