passage of the northwest Pacific extending northeast from the East China Sea to the Sea of Japan (East Sea) between the south coast of the Korean peninsula (northwest) and the Japanese islands of Kyushu and Honshu. The strait, which is 300 feet (90 m) deep, is bisected by the Tsushima islands, the passage to the east being often referred to as Tsushima Strait. The western channel was formerly called the Chōsen Strait.

The warm Tsushima Current, a branch of the Kuroshio (Japan Current), passes north through the strait. Following the coasts of the Japanese islands, some of the current's waters continue north to flow into the Pacific and the Sea of Okhotsk at Sakhalin Island, while the remainder swirls counterclockwise to flow south along the Asian mainland. In 1905, during the Russo-Japanese War, a Japanese fleet annihilated a Russian force in the Battle of Tsushima (Tsushima, Battle of) Strait.