Seto Inland Sea

This article needs additional citations for verification. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. Find sources: "Seto Inland Sea" – news · newspapers · books · scholar · JSTOR (May 2010) (Learn how and when to remove this message)

Seto Inland Sea
View of the Seto Inland Sea from Miyajima island
Seto Inland Sea
The Inland Sea and its major straits
Location	Pacific Ocean
Coordinates	34°10′N 133°20′E / 34.167°N 133.333°E / 34.167; 133.333
Type	Sea
Basin countries	Japan
Surface area	23,203 km2 (9,000 sq mi)
Average depth	38 m (125 ft)

The Seto Inland Sea (瀬戸内海, Seto Naikai), sometimes shortened to the Inland Sea, is the body of water separating Honshu, Shikoku, and Kyushu, three of the four main islands of Japan. It serves as a waterway connecting the Pacific Ocean to the Sea of Japan. It connects to Osaka Bay and provides a sea transport link to industrial centers in the Kansai region, including Osaka and Kobe. Before the construction of the San'yō Main Line, it was the main transportation link between Kansai and Kyūshū.

Yamaguchi, Hiroshima, Okayama, Hyōgo, Osaka, Wakayama, Kagawa, Ehime, Tokushima, Fukuoka, and Ōita prefectures have coastlines on the Seto Inland Sea; the cities of Hiroshima, Iwakuni, Takamatsu, and Matsuyama are also located on it.

The Setouchi region encompasses the sea and surrounding coastal areas. The region is known for its moderate climate, with a stable year-round temperature and relatively low rainfall levels. The sea is famous for its periodic red tides (赤潮, akashio) caused by dense groupings of certain phytoplankton that result in the death of large numbers of fish. Since the 1980s, the sea's northern and southern shores have been connected by the three routes of the Honshū–Shikoku Bridge Project, including the Great Seto Bridge, which serves both railroad and automobile traffic.