Bungo-ōno (豊後大野市 Bungo-ōno-shi) is a city located in Ōita Prefecture, Japan. The modern city of Bungo-ōno was established on March 31, 2005, from the merger between the towns of Asaji, Inukai, Mie, Ogata and Ōno, and the villages of Chitose and Kiyokawa (all from Ōno District). As of January 31, 2012, the city has an estimated population of 40,104, with 16,484 households and a population density of 66.47 persons per km². The total area is 603.36 km². In 2012, the growing deer population began to greatly affect the shiitake mushroom farming industry.