The Tsushima Strait (対馬海峡) is a strait between the Korean Peninsula and Kyushu, the furthest west of the four largest islands in Japan. It connects the East China Sea and the Sea of Japan. The Japanese island Tsushima separates the strait into the West Channel (Korea Strait), between Tsushima Island and Korea, and the East Channel, between Tsushima Island and Kyushu.

This sea serves as a stage for cultural exchange between Korea and Japan. Buddhism was transmitted from Korea to Japan through this strait. The Mongolian invasion of Japan crossed this sea and the Korean Allied Forces have attacked Japan through it. A decisive battle between the Japanese and Russian navies during the Russo-Japanese War also took place here. A ferry service operates between Busan and Shimonoseki now, and Korean and Japanese passengers are going back and forth.