The Onagawa Nuclear Power Plant genshiryoku hatsudensho, Onagawa NPP) is a nuclear power plant located on a 1,730,000 m2 site in Onagawa in the Oshika District and Ishinomaki city, Miyagi Prefecture, Japan. It is managed by the Tohoku Electric Power Company. It was the most quickly constructed nuclear power plant in the world.

Onagawa is a town located in Miyagi Prefecture, Japan. As of 30 April 2020, the town had an estimated population of 6,319, and a population density of 97 persons per km2 in 3,110 households. The total area of the town is 65.35 square kilometres (25.23 sq mi).