The Korea Strait is a sea passage in East Asia between the Korean Peninsula and Japan.

It is economically important, as many shipping lanes pass through the strait, and both Japan and South Korea allow free passage through it.

The water-mass characteristics vary widely because of the low-salinity waters of the southeast coasts of Korea and China.

Numerous international shipping lanes pass through the strait, including those carrying much of the traffic bound for the ports of southern South Korea.

Both South Korea and Japan have restricted their territorial claims in the strait to 3 nautical miles (5.6 km) from shore, so as to permit free passage through it.

Commercial ferries run from South Korean Busan, Geoje to Japanese ports including Fukuoka, Tsushima, Shimonoseki, and Hiroshima.

Japan's territorial waters extend to three nautical miles (5.6 km) into the strait instead of the usual twelve, reportedly to allow nuclear-armed United States Navy warships and submarines to transit the strait without violating Japan's prohibition against nuclear weapons in its territory.