Okayama Prefecture borders Hyogo Prefecture, Tottori Prefecture and Hiroshima Prefecture.
On March 31, 2005, the town of Hokubo from Jobo District and the towns of Katsuyama, Ochiai, Yubara, and Kuse and the villages of Mikamo, Kawakami, Yatsuka, and Chuka (all from Maniwa District) merged to form the new city of Maniwa.
On March 31, 2005, the town of Katsuta from Katsuta District and the towns of Ohara, Mimasaka, Sakuto, and Aida and the village of Higashiawakura (all from Aida District) merged to form the new city of Mimasaka.
The towns of Okutsu and Kagamino and the villages of Kamisaibara and Tomi were merged to form the new town of Kagamino.
The towns of San'yo, Akasaka, Yoshii (in Akaiwa District), and Kumayama were merged to form the city of Akaiwa.
The towns of Hokubo, Katsuyama, Ochiai, Yubara, and Kuse and the villages of Mikamo, Kawakami, Yatsuka, and Chuka were merged to form the city of Maniwa.