The , also known as the region, is the westernmost region of Honshà «, the largest island of Japan. It consists of the prefectures of Hiroshima, Okayama, Shimane, Tottori and Yamaguchi. As of the 2020 census, it has a population of 7,328,339.
Chà «goku literally means "middle country", but the origin of the name is unclear. Historically, Japan was divided into a number of provinces called koku, which were in turn classified according to both their power and their distances from the administrative center in Kansai. Under the latter classification, most provinces are divided into , , and . Therefore, one explanation is that Chà «goku was originally used to refer to the collection of "middle countries" to the west of the capital. However, only five (fewer than half) of the provinces normally considered part of Chà «goku region were in fact classified as middle countries, and the term never applied to the many middle countries to the east of Kansai. Therefore, an alternative explanation is that Chà «goku referred to provinces between Kansai and Kyà «shà «, which was historically important as the link between Japan and mainland Asia.
Historically, Chà «goku referred to the 16 provinces of and , which led to the region's alternative name described below. However, because some of the easternmost provinces were later subsumed into prefectures based primarily in Kansai, those areas are, strictly speaking, not part of the Chà «goku region in modern usage.
In Japanese, the characters and the reading Chà «goku are also used to mean "China". The same characters are used in Chinese to refer to China, but pronounced Zhà Ângguó in Mandarin, lit. "Middle Kingdom" or "Middle Country" (Wade Giles: Chung<sup>1</sup>-kuo<sup>2</sup>). It is similar to the use of the West Country in English for a region of England. However, before the end of the Second World War, China was more commonly called in order to avoid confusing the Chà «goku region. Due to the extensive use of this word during the Sino-Japanese War, the term shina has become an offensive word and was abandoned thereafter, and Chà «goku has since then been used instead of shina. In modern times, primarily in the tourism industry, for the same purpose, the Chà «goku region is also called the "San'inâÂÂSan'yà  region". San'in ("yin of the mountains") is the northern part facing the Sea of Japan. San'yà  ("yang of the mountains") is the southern part facing the Seto Inland Sea. These names were created using the yin and yangâÂÂbased placeâÂÂnaming scheme.
The city of Hiroshima, the "capital" of the Chà «goku region, was rebuilt after being destroyed by an atomic bomb in 1945, and is now an industrial metropolis of more than one million people.
Overfishing and pollution reduced the productivity of the Inland Sea fishing grounds; and San'yo is an area concentrated on heavy industry. In contrast, San'in is less industrialized with an agricultural economy.
The Chà «goku region consists of the following prefectures: Hiroshima, Yamaguchi, Shimane, and Tottori. Okayama is also included, although only Bitchà « Province was considered a "middle country" (ä¸Âå½); Mimasaka Province and Bizen Province, the other two components of modern-day Okayama, were considered "near countries" (è¿Âå½). Kyà «shà «, Shikoku, and Kansai neighbor the Chà «goku region.
The Chà «goku region is characterized by irregular rolling hills and limited plain areas and is divided into two distinct parts by mountains running east and west through its center.
The two largest metropolitan areas in Chà «goku region are Hiroshima and Okayama whose total population of the two metropolitan areas amount to 2.808 million as of 2020. Their Urban Employment Area amounts to around 3 million people for the Chà «goku region. The rest of Chà «goku region is sparsely populated and very rural.
Per Japanese census data, the Chà «goku region as a whole has experienced a steady population decline since 1992, with some prefectures within the region experiencing declines since 1985. The region reached a peak population of roughly 7.8 million in 1991.
The region's largest airport is Hiroshima Airport which is located east of Hiroshima, there are also smaller airports across the regions including Iwami Airport, Izumo Airport, Okayama Airport, Yonago Kitaro Airport, Oki Airport, Tottori Airport, and Yamaguchi Ube Airport.