is a town located in Kanagawa Prefecture, Japan. , the town had an estimated population of 31,262 and a population density of 1820 persons per km². The total area of the town is . Geography Ōiso is located on the coastline of central Kanagawa Prefecture, facing Sagami Bay of the Pacific Ocean. The area is generally hilly, rising to Mount Koma (168 metres) in the northwest of the centre of town. The coastline of Ōiso is sandy and is regarded as the western end of the Shōnan area. Ōiso remains a popular beach resort and holiday spot for residents of Tokyo. Surrounding municipalities Kanagawa Prefecture Hiratsuka Ninomiya Climate Ōiso has a Humid subtropical climate (Köppen Cfa) characterized by warm summers and cool winters with light to no snowfall. The average annual temperature in Ōiso is 15.8 °C. The average annual rainfall is 2144 mm with September as the wettest month. The temperatures are highest on average in August, at around 25.7 °C, and lowest in January, at around 5.2 °C. Demographics Per Japanese census data, the population of Ōiso has grown steadily over the past century, with a slight drop from 2010 to 2020. History Ōiso is the ancient centre of Sagami Province. The exact location of the Nara period provincial government of Sagami Province is unknown, but tradition and the place name "Kōzu" place its probable location within the boundaries of present-day Ōiso. As a minor coastal settlement, Ōiso was under the control of the later Hōjō clan of Odawara during the Sengoku period. In the Edo period, it was nominally part of Odawara Domain, and developed as Ōiso-juku, a post town on the Tōkaidō connecting Edo with Kyoto. After the Meiji Restoration and with the establishment of the district system in 1878, it came under the control of . Ōiso became a town on 1 April 1889 with the creation of the modern municipalities system. Blessed with a temperate climate, and with convenient access to Tokyo due to the Tōkaidō Main Line railway, it was favoured as a seaside health resort by politicians and literary figures during the Meiji period after a glowing report on its location was written by noted physician Matsumoto Jun. Prime Minister Itō Hirobumi, Yamagata Aritomo, Saionji Kinmochi and Ōkuma Shigenobu, Foreign Minister Mutsu Munemitsu, writer Shimazaki Toson and zaibatsu founder Yasuda Zenjirō had summer residences in Ōiso. This popularity continued into the postwar