The city area, which is the largest in the prefecture, is long from north to south, facing the Seto Inland Sea (Yamaguchi Bay) at the south end, and bordering Shimane Prefecture at the north end.

The Ōuchi clan claimed descent from the royal house of Baekje and grew wealthy due to extensive trade with Korea and Ming Dynasty China.

After the Onin War, they welcomed intellectuals who escaped from Kyoto, such that Yamaguchi prospered as a center of culture.

Later in the Muromachi period, Christian missionaries from Spain and Portugal were welcomed, and the area became an early center for the Kirishitan faith.

The Ōuchi were eventually overthrown by their vassals, the Mōri clan, who ruled the area as part of Chōshū Domain during the Edo Period.

On April 1, 1944, Yamaguchi annexed towns of Ogōri and Ajisu, and the villages of Hirakawa, Ōtoshi, Sue, Natajima, Aiofutajima, Kagawa and Sayama (all from Yoshiki District.)

Yamaguchi has a mayor-council form of government with a directly elected mayor and a unicameral city council of 35 members.