Setouchi (瀬戸内市, Setouchi-shi) is a city located in southern Okayama Prefecture, Japan.

It faces the Seto Inland Sea to the south, and the coastline is intricate and forms part of the Setonaikai National Park.

Fukuoka District, which flourished as a trade center and later a political center along the Seto Inland Sea until the beginning of the Edo period, served by the Yoshii River and the Seto Inland Sea, is also included as a part of the city.

In the middle Muromachi period, the daimyō who governed Bizen province took this castle as their site, rebuilt and fortified it more than before.

Setouchi has a mayor-council form of government with a directly elected mayor and a unicameral city council of 18 members.

In terms of national politics, the city is part of the Okayama 2nd district of the lower house of the Diet of Japan.

Setouchi has a mixed economy, based on agriculture, (rice, pumpkins, cabbage, mushrooms, olives), commercial fishing (aquaculture of oysters) and industry.