Ōkunoshima (Japanese: 大久野島) is a small island in the Inland Sea of Japan. It is considered to be part of the city of Takehara, Hiroshima Prefecture. It is accessible by ferry from Tadanoumi and Ōmishima. There are campsites, walking trails and places of historical interest on the island. It is often called Usagi Shima (うさぎ島, "Rabbit Island") because of the large population of free-ranging domestic rabbits that roam the island. The rabbits have been habituated and will approach humans.
Ōkunoshima played a key role during the Second Sino-Japanese War as a poison gas factory for much of Japan's chemical warfare carried out in China.