|Native name: Кетой
NASA picture of Ketoy Island
|Location||Sea of Okhotsk|
|Area||73 km2 (28 sq mi)|
|Highest elevation||1,172 m (3,845 ft)|
|Ethnic groups||Ainu (formerly)|
The island is a complex stratovolcano lined with steep cliffs ranging from 30 metres to 60 metres on the east and south sides with the west and north being taller. The beaches on the island consist of boulders and stones. In the centre of the island is a 1.5 km wide caldera filled by a freshwater caldera lake. The terrain is undulating and steep with numerous hills, rising to two main peaks:
- Ketoy -(Russian: влк Кетой; Japanese 計吐夷岳; Ketoidake) with a height of 1,172 meters  to the east of the central caldera lake
- Pallas -(Russian: влк Палласа; Japanese 白烟山; Shirokemuriyama) with a height of 993 meters in the center of the island. Pallas also has a caldera lake, with diameters of approximately 550 meters.
Ketoy had no permanent habitation prior to European contact, but was visited in summer by the Ainu tribes from Rasshua for hunting. Claimed by the Empire of Russia, sovereignty was passed to the Empire of Japan per the Treaty of Saint Petersburg (1875) along with the rest of the Kuril islands. The island was formerly administered as part of Shimushiro District of Nemuro Subprefecture of Hokkaidō. After World War II, the island came under the control of the Soviet Union, and is now administered as part of the Sakhalin Oblast of the Russian Federation.
- Gorshkov, G. S. Volcanism and the Upper Mantle Investigations in the Kurile Island Arc. Monographs in geoscience. New York: Plenum Press, 1970. ISBN 0-306-30407-4
- Krasheninnikov, Stepan Petrovich, and James Greive. The History of Kamtschatka and the Kurilski Islands, with the Countries Adjacent. Chicago: Quadrangle Books, 1963.
- Rees, David. The Soviet Seizure of the Kuriles. New York: Praeger, 1985. ISBN 0-03-002552-4
- Takahashi, Hideki, and Masahiro Ōhara. Biodiversity and Biogeography of the Kuril Islands and Sakhalin. Bulletin of the Hokkaido University Museum, no. 2-. Sapporo, Japan: Hokkaido University Museum, 2004.
- "International Kuril Island Project（IKIP）". University of Washington Fish Collection or the respective authors.
- "Global Volcanism Program". Smithsonian National Museum of Natural History.
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