Tsushima is an island city located in the Nagasaki Prefecture of Japan. It serves as the sole city within the Tsushima Subprefecture and encompasses the entirety of Tsushima Island. The island is situated in the Tsushima Strait, positioned north of Nagasaki on the western side of Kyushu, which is the southernmost mainland island of Japan.
The city covers a total area of 708.61 km², accounting for approximately 17.3% of the total area of Nagasaki Prefecture. As of March 2017, Tsushima had an estimated population of 31,550 residents, resulting in a population density of 45 persons per square kilometer.