Tsushima Strait or Eastern Channel (동수로 Dongsuro) is a channel of the Korea Strait, which lies between Korea and Japan, connecting the Sea of Japan, the Yellow Sea, and the East China Sea.
The strait is the channel to the east and southeast of Tsushima Island, with the Japanese islands of Honshu to the east and northeast, and Kyushu and the Gotō Islands to the south and southeast. It is narrowest south-east of Shimono-shima, the south end of Tsushima Island proper, constricted there by nearby Iki Island, which lies wholly in the strait near the tip of Honshu. South of that point Japan's Inland Sea mingles its waters through the narrow Kanmon Strait between Honshu and Kyushu, with those of the Eastern Channel, making for some of the busiest sea lanes in the world.
The Strait was the site of the decisive naval battle in the Russo-Japanese War, the Battle of Tsushima, between the Japanese and Russian navies in 1905; in which the Russian fleet was virtually destroyed.
The Tsushima Strait measures approximately 100 kilometres along Tsushima Island and is about 65 kilometres wide at its narrowest. The strait has a depth of about 140 metres and is bounded by the Tsushima Islands to the west through north (of Gotō Islands). Nearby Iki Island lies in the strait about 50 kilometres towards Kyūshū from the southern tip of Kamino-shima (South Island).
A warm branch of the Kuroshio Current passes through the strait. Originating along the Japanese islands, this current passes through the Sea of Japan then a branch eventually flowing into the Northern Pacific Ocean via the Tsugaru Strait south of Hokkaido. Another branch continues far northward and divides along either shore of Sakhalin Island; eventually flowing into the Sea of Okhotsk via the La Perouse Strait north of Hokkaido and via the Strait of Tartary into the Sea of Okhotsk north of Sakhalin Island near Vladivostok.
The Kuroshio Current brings rich fisheries resources from the East China Sea into the Sea of Japan, like Japanese amberjack, Japanese horse mackerel, but these days also brings disaster like mass aggregation of gigantic Nomura's jellyfish and waste from countries along the course of the current.