Tsunoshima (角島) is an island located in the Sea of Japan. Located in the north west of Yamaguchi Prefecture, it is a part of Shimonoseki city. The island has an area of 4.1 square kilometers (1.6 sq mi) and has a coastline of 17.1 kilometres (10.6 mi). The island consists primarily of basalt, and is a part of the Kita-Nagato Kaigan Quasi-National Park. As of 28 August 2008, the population of Tsunoshima stood at 907.