The Nishiseto Expressway (西瀬戸自動車道, Nishiseto Jidōsha-dō), often called the Shimanami Kaidō (しまなみ海道) is an expressway in Japan that connects Onomichi, Hiroshima and Imabari, Ehime, going through nine of the Geiyo Islands, including Ōshima, Umashima, and Innoshima. The road and multiple bridge crossing across the Seto Inland Sea is one of the three main transportation links of the Honshū–Shikoku Bridge Project constructed between the islands of Honshu and Shikoku.
The expressway contains fifty-five bridges, including the Kurushima Kaikyō Bridge, the world's longest series of suspension bridges, and the Tatara Bridge, the world's fourth longest cable-stayed bridge. The route is famed for its scenic views and can be crossed by bicycles, mopeds and pedestrians as well as cars. It was opened on May 1, 1999, and is 59.4 kilometres (36.9 miles) long, sporting four lanes with a separated path for pedestrians and cyclists.