Tsushima Island (対馬 Tsushima) is an island of the Japanese archipelago situated in the Korea Strait between the Japanese mainland and the Korean Peninsula. The main island of Tsushima was once a single island but was divided into two in 1671 by the Ōfunakoshiseto canal and into three in 1900 by the Manzekiseto canal. These canals were driven through isthmuses in the center of the island, creating North Tsushima Island (Kamijima) and South Tsushima Island (Shimojima). Tsushima also incorporates over 100 smaller islands (many tiny). The name Tsushima generally refers to all the islands collectively.
The island group measures about 70 km (43 mi) by 15 km (9 mi) and has a population of about 34,000 as of 2013. The main islands (that is, the "North" and "South" islands, and the thin island that connects them) are the largest coherent satellite island group of Nagasaki Prefecture and the fourth largest in Japan (excluding Honshu, Kyushu, Shikoku and Hokkaido). The city of Tsushima lies on the Tsushima islands, and is divided into six boroughs.