Oshima Shipbuilding Co., Ltd. is a privately held Japanese shipbuilding company. The company was founded on February 7, 1973, and began operations in June 1974. It is a joint venture between Sumitomo Corporation, Sumitomo Heavy Industries, and the Daizo Corporation.

Saikai is a city located in Nagasaki Prefecture, Japan. As of March 2017, the city has an estimated population of 28,815 and a population density of 4,700 persons per km2. The total area is 242.01 km2.