Okayama is the capital city of Okayama Prefecture in the Chūgoku region of Japan. The Okayama metropolitan area, centered around the city, has the largest urban employment zone in the Chugoku region of western Japan. The city was founded on June 1, 1889. As of February 2023, the city has an estimated population of 700,940 and a population density of 890 persons per km2. The total area is 789.95 square kilometres.

The Seto Inland Sea , sometimes shortened to the Inland Sea, is the body of water separating Honshu, Shikoku, and Kyushu, three of the four main islands of Japan. It serves as a waterway connecting the Pacific Ocean to the Sea of Japan. It connects to Osaka Bay and provides a sea transport link to industrial centers in the Kansai region, including Osaka and Kobe. Before the construction of the San'yō Main Line, it was the main transportation link between Kansai and Kyūshū.