Kamiamakusa (上天草市, Kamiamakusa-shi) is a city located in Kumamoto Prefecture, Japan. As of 31 July 2024, the city had an estimated population of 23,824 in 11085 households, and a population density of 190 persons per km. The total area of the city is 126.67 km (48.91 sq mi).

Kamiamakusa covers the western coast of one of the two main islands, Kamishima (上島, "Upper Island") and ten smaller inhabited islands (including Ōyano-jima) and numerous uninhabited islets located the central-west Kumamoto Prefecture, in between the Yatsushiro Sea and the East China Sea. Parts of the city are within the borders of the Unzen-Amakusa National Park.

Kumamoto Prefecture

• Amakusa
• Uki

Kamiamakusa has a humid subtropical climate (Köppen climate classification Cfa) with hot, humid summers and cool winters. There is significant precipitation throughout the year, especially during June and July. The average annual temperature in Kamiamakusa is 16.8 °C (62.2 °F). The average annual rainfall is 2,019.9 mm (79.52 in) with June as the wettest month. The temperatures are highest on average in August, at around 27.5 °C (81.5 °F), and lowest in January, at around 6.5 °C (43.7 °F). The highest temperature ever recorded in Kamiamakusa was 37.2 °C (99.0 °F) on 13 August 2018; the coldest temperature ever recorded was −6.5 °C (20.3 °F) on 25 January 2016.

Per Japanese census data, the population of Kamiamakusa in 2020 is 24,563 people. Kamiamakusa has been conducting censuses since 1920.

Historical population

Year Pop. ±% 1920 39,984 —     1925 39,622 −0.9% 1930 41,036 +3.6% 1935 42,157 +2.7% 1940 41,103 −2.5% 1945 54,951 +33.7% 1950 55,050 +0.2% 1955 53,921 −2.1% 1960 51,439 −4.6% 1965 47,914 −6.9% 1970 42,136 −12.1%	Year Pop. ±% 1975 41,541 −1.4% 1980 40,682 −2.1% 1985 39,900 −1.9% 1990 38,316 −4.0% 1995 36,667 −4.3% 2000 35,314 −3.7% 2005 32,502 −8.0% 2010 29,901 −8.0% 2015 27,006 −9.7% 2020 24,563 −9.0%
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Kami-Amakusa population statistics

The area of Kamiamakusa was part of ancient Higo Province, During the Edo Period it was tenryō territory under direct control of the Tokugawa shogunate and administered from the office of the Nagasaki bugyō.

The city of Kamiamakusa was established on March 31, 2004, from the merger of the towns of Himedo, Matsushima, Ōyano and Ryūgatake (all from Amakusa District).

Kamiamakusa has a mayor-council form of government with a directly elected mayor and a unicameral city council of 16 members. Kamiamakusa contributes one member to the Kumamoto Prefectural Assembly. In terms of national politics, the city is part of the Kumamoto 4th district of the lower house of the Diet of Japan.

Kamiamakusa has a mixed economy dominated by agriculture, commercial fishing and light manufacturing. Tourism also plays a major role.

Kamiamakusa has 11 public elementary schools and six public junior high schools operated by the city government and one public high school operated by the Kumamoto Prefectural Board of Education.

Kamiamakusa has no passenger railway service. The nearest train station is Misumi Station on the JR Kyushu Misumi Line in Uki City.

• National Route 266
• National Route 324

• Five Bridges of Amakusa
• Unzen-Amakusa National Park

• Amakusa Shirō - The leader of the Shimabara Rebellion in 1638.

• Media related to Kamiamakusa, Kumamoto at Wikimedia Commons
• Kami-Amakusa City official website (in Japanese)