Isahaya (諫早市, Isahaya-shi) is a city located in Nagasaki Prefecture, Japan. As of June 1, 2024, the city had an estimated population of 131,467 in 55169 households, and a population density of 380 people per km2.[1] The total area of the city is 341.79 km2 (131.97 sq mi) Located in the central part of Nagasaki Prefecture, Isahaya is surrounded by the ocean on three sides and the Tara mounts to the north. To the west is the base of the Nagasaki Peninsula and to the south is the base of Shimabara Peninsula. The city area faces Ōmura Bay in the northwest, Ariake Sea (Isahaya Bay) on the east and Tachibana Bay on the south. Major land reclamation projects have occurred which added plains to the Ariake Sea. The biggest is the Isahaya Bay reclamation project (諫早湾干拓事業) by the Ministry of Agriculture, Forestry and Fisheries that started in 1989. Embankments and sluice gates were built and a total of 35 km2 has been reclaimed as of 2018. Nagasaki Prefecture