The Oki Islands are volcanic in origin, and are the exposed eroded summits of two massive stratovolcanoes dating approximately 5 million years ago to the Tertiary and Quaternary periods. The oldest rocks in Japan have been found on the Oki Islands.
Dōgo to the east is the largest island in area, and has the highest elevation, Mount Daimanji, at 608 metres (1,995 ft) above sea level. The Dōzen group of islands to the west are all portions of single ancient volcanic caldera which collapsed, leaving three large islands (Nishinoshima, Nakanoshima and Chiburijima) and numerous smaller islands and rocks in a ring formation surrounding a central lagoon. The archipelago is approximately 80 kilometres (43 nmi) north of Honshu coast at its closest point. For administrative purposes, the Japanese government officially considers the disputed islet of Liancourt Rocks (Dokdo or Takeshima) to be a part of the town of Okinoshima on Dōgo.
The Oki Islands have been inhabited since the Japanese Paleolithic era, and numerous artifacts from the Jōmon, Yayoi and Kofun periods have been found by archaeologists, indicating continuous human occupation and activity. The island were organized as Oki Province under the Ritsuryō reforms in the latter half of the seventh century, and the name “Oki-no-kuni” appears on wooden markers found in the imperial capital of Nara. The island of Dōgo is mentioned in the Nara period chronicles Kojiki and Nihon Shoki, and Dōgo Island was the location of the capital of ancient Oki Province. During the late Heian period, due to its remoteness, Oki Province came to known as a place for political exile. In 1221, Emperor Go-Toba was sent to Oki, and died in exile on the islands; In 1332, Emperor Go-Daigo was also sent in exile to Oki, but later managed to escape and regain control of the country.
From the Kamakura period Oki Province was governed primarily by the shugo of Izumo Province. In the Muromachi period, it was ruled successively by the Sasaki clan, the Yamana clan and the Kyōgoku clan. In the Sengoku period the Amago clan held this province. After the Amago fell and the Tokugawa shogunate was established, Oki Province was declared a tenryō dominion under the direct control of the Shogun. The daimyō of Matsue Domain, belonging to the Matsudaira clan, was appointed as governor.
The entire province had an assessed revenue of only 18,000 koku, although its actual revenues were closer to only 12,000 koku. The province was a frequent port of call for the Kitamaebune coastal trading ships during the Edo period.
Following the Meiji Restoration, Oki Province became "Oki Prefecture" from February to June 1869. It was then attached to Tottori Prefecture until 1876, when it was transferred to Shimane Prefecture.
In 1892, Lafcadio Hearn visited the islands, spending a month there, and writing about his experiences in Glimpses of Unfamiliar Japan. Oki was visited by the American naturalist Charles Henry Gilbert in 1906.
The population is approximately 24,500 inhabitants spread over the four municipalities of:
Oki Airport (airport code "OKI") lies on the southeastern part of Dōgo and provides air service to Osaka International Airport (Itami, "ITM") and Izumo Airport ("IZO").
The Oki islands can be reached by ferries from harbours like Sakaiminato, Shichirui and Kaga on the mainland. There are also frequent ferries operating between the Dōzen islands throughout the year.