Tsushima Island is an island of the Japanese archipelago situated in-between the Tsushima Strait and Korea Strait, approximately halfway between Kyushu and the Korean Peninsula. The main island of Tsushima, once a single island, 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, forming "North Tsushima Island" (Kamino-shima) and "South Tsushima Island" (Shimono-shima). Tsushima also incorporates over 100 smaller islands, many tiny. The name Tsushima generally refers to all the islands of the Tsushima archipelago collectively. Administratively, Tsushima Island is in Nagasaki Prefecture.

Nagasaki Prefecture is a prefecture of Japan located on the island of Kyūshū. Nagasaki Prefecture has a population of 1,314,078 and has a geographic area of 4,130 km2. Nagasaki Prefecture borders Saga Prefecture to the northeast.