Surrounded by the Suo Channel and Honshu Island to the north, the Iyo Channel and Shikoku Island to the east, it is bordered by Miyazaki Prefecture to the south, and Fukuoka Prefecture and Kumamoto Prefecture to the west.
On October 1, 2005, the city of Kitsuki and the village of Ota from Nishikunisaki District and the town of Yamaga from Hayami District merged to form the city of Kitsuki.
Oita Prefecture is famous for its hot springs, particularly those in and around the city of Beppu, known as the 'hells', or jigoku.