Tsugaru Strait

The Tsugaru Strait (津軽海峡, Tsugaru Kaikyō) is a strait between Honshu and Hokkaido in northern Japan connecting the Sea of Japan with the Pacific Ocean. It was named after the western part of Aomori Prefecture. The Seikan Tunnel passes under it at its narrowest point, 12.1 miles (19.5 km) between Tappi Misaki on the Tsugaru Peninsula in Aomori Prefecture, Honshu, and Shirakami Misaki on the Matsumae Peninsula in Hokkaido.

Japan's territorial waters extend only three nautical miles (5.6 km) into the strait, allowing nuclear-armed United States Navy warships and submarines to pass through without violating Japan's laws against nuclear weapons. The part of the strait in international waters is still within Japan's exclusive economic zone, and the Seikan Tunnel remains under Japanese control.

The Tsugaru Strait has two parts, both about 20 km across, with depths of up to 200 meters. Ferry services, such as the Tsugaru Kaikyō Ferry and the Seikan ferry, operate across the strait.

The strait is also important in nature. Thomas Blakiston, an English explorer, noticed that animals in Hokkaido are related to those in northern Asia, while those on Honshu are related to southern Asian species. This made the Tsugaru Strait a key boundary in animal geography, known as Blakiston's Line.