日本原子力研究開発機構
is a town located in Ibaraki Prefecture, Japan. , the town had an estimated population of 15,867 in 6,881 households and a population density of . The percentage of the population aged over 65 was 34.0%. The total area of the town is . The Japan Atomic Energy Agency operates a research center in Ōarai with a number of nuclear research reactors, including the Jōyō and High-temperature engineering test reactor facilities.