Usa is a city located in Ōita Prefecture, Japan. As of 30 November 2023, the city had an estimated population of 52,808 in 26026 households, and a population density of 120 persons per km2. The total area of the city is 439.05 km2 (169.52 sq mi). It is notable for Usa Jingū, the head shrine of all 40,000 Hachiman shrines across Japan; the city annually attracts as many as 1.8 million worshipers from all over the country on New Year's Day.

Ōita Prefecture is a prefecture of Japan located on the island of Kyūshū. Ōita Prefecture has a population of 1,136,245 and has a geographic area of 6,340 km2. Ōita Prefecture borders Fukuoka Prefecture to the northwest, Kumamoto Prefecture to the southwest, and Miyazaki Prefecture to the south.