Yeosu or Yosu (yôˈsōˈ) [key], city (1995 pop. 183,559), South Jeolla (Cholla) prov., S South Korea, on the Korea Strait. The municipality consists of a peninsula and more than 300 neighboring islands. It is a trading port and fishing base and the site of a large oil refinery. Yeosu also has an important thermal power plant. The city was the site of an international exposition in 2012. A campus of Chonnam National Univ. is there.