Yamaguchi Prefecture is a prefecture of Japan located in the Chūgoku region of Honshu. Yamaguchi Prefecture has a population of 1,377,631 and has a geographic area of 6,112 km2. Yamaguchi Prefecture borders Shimane Prefecture to the north and Hiroshima Prefecture to the northeast.

The Chūgoku region , also known as the San'in-San'yō region, is the westernmost region of Honshū, the largest island of Japan. It consists of the prefectures of Hiroshima, Okayama, Shimane, Tottori and Yamaguchi. In 2010, it had a population of 7,563,428.