is a city located in Yamaguchi Prefecture, Japan. , the city had an estimated population of 59,867 in 29122 households and a population density of 530 persons per km². The total area of the city is .

Geography
San'yō-Onoda is located in the southwestern part of Yamaguchi Prefecture. It is long in the north-south direction and has a fan shape that opens to the Seto Inland Sea. The Asa River flows from the north to the central area, and the Ariho River flows from the northeast to the east, flowing south into the Seto Inland Sea. The city hall is located on the west bank of the Ariho River mouth.

Neighbouring municipalities 
Yamaguchi Prefecture
 Ube
 Shimonoseki
  Mine

Climate
San'yō-Onoda has a humid subtropical climate (Köppen climate classification Cfa) with very warm summers and cool winters.  The average annual temperature in Hikari is 16.3 °C. The average annual rainfall is 1732 mm with September as the wettest month. The temperatures are highest on average in July, at around 27.1 °C, and lowest in January, at around 6.4 °C.

Demographics
Per Japanese census data, the population of San'yō-Onoda peaked in the 1960s, and has remained relatively steady since the 1970s

History
The area of San'yō-Onoda was part of an ancient Nagato Province. During the Edo Period, the area was part of the holdings of Chōshū Domain. Following the Meiji restoration, the villages of Asai, Sue, and Takachiho  were established within Asa District, Yamaguchi  with the creation of the modern municipalities system on April 1, 1889. Asai became the town of Asa on October 1, 1918 and Sue was elevated to town status on April 3, 1920 and renamed Onoda. Takachiho was elevated to town status on April 1, 1938 and merged with Onoda on November 3, 1940 to become the city of Onoda. Asa merged with the town of Habu to form the town of San'yō on September 30, 1956. Onoda and San'yo merged to form the city of San'yō-Onoda on March 22, 2005.

Government
San'yō-Onoda has a mayor-council form of government with a directly elected mayor and a unicameral city council of 22 members. San'yō-Onoda contributes three members to the Yamaguchi Prefectural Assembly. In terms of national politics, the city is part of the Yamaguchi 3rd district of the lower house of the Diet of Japan.

Economy
San'yō-Onoda is an industrial city centered on the chemical industry based on cement and oil refining. Along with neighboring Ube, it is part of the Setouchi industrial area.

Education
San'yō-Onoda has 13 public elementary school and six public junior high schools operated by the city government, and three public high schools operated by the Yamaguchi Prefectural Board of Education.  There are also one  private high school. The city operated San'yō-Onoda City University (formerly the Tokyo University of Science, Yamaguchi) is located in San'yō-Onoda

Transportation

Railway 
 JR West (JR West) - San'yō Shinkansen
  
 JR West (JR West) - San'yō Main Line
  -  -  
 JR West (JR West) - Onoda Line (Main line)
  -  -  -  -  - 
 JR West (JR West) - Onoda Line (Motoyama branch line)
  -  - 
 JR West (JR West) - Mine Line 
  -

Highways 
  San'yō Expressway
  Chugoku Expressway

Sister city relation
  Chichibu, Saitama, Japan since May 20, 1996
  Moreton Bay, Australia since August 18, 1992

Notable people from San'yō-Onoda
Yohei Kurakawa, Japanese football player
Aoki Shūzō, former Foreign Minister in Meiji period Japan
Minoru Fujita, Japanese professional wrestler

References

External links

 San'yō-Onoda official website 
 San'yō-Onoda official website 

Cities in Yamaguchi Prefecture
Port settlements in Japan
Populated coastal places in Japan
San'yō-Onoda